Assumption of infallibility

I present here a somewhat more formal version of the famous “assumption of infallibility” argument from J.S. Mill’s On Liberty, with the conclusion that “it is never rational for a man, or government, to silence discussion of some opinion.”

I first shared it with others in 2020-07-23, in a Facebook group that is no longer active. At that time, I often made such versions of philosophical arguments I had found and shared them with that group, so that, with the all the premises distinguished and numbered, people could state their objections more precisely in the comments. It was a great learning experience.

This is probably my best work from that period, in terms of how much easier it is to follow than the corresponding original text. Five premises are asserted, and the conclusion is supposed to be deduced from them. After the formalization, I list the textual support that I had gathered for each premise, all of which was taken from the second chapter of Mill’s work. This is all unchanged from how it was first written in 2020, since I do not wish to read Mill’s work again to think more carefully about the quality of the formulation. After this, there will be some comments on the argument.

The argument

1. Every man well knows himself to be fallible. It is irrational to deny this.

2. Given that we are fallible, we are only justified in assuming one of our opinions as true for the purposes of action if we allow others complete liberty of contradicting and disproving it.

3. (a) A man, or government, who silences discussion of some opinion because he thinks it is false, is acting upon his belief that the opinion is false, and his belief depends upon reference to the opinion. (b) A man, or government, who silences discussion of some opinion for some other reason than it being false, such as it being useful to silence it, is also acting upon a belief of his which depends upon reference to the opinion the discussion of which he is silencing, such as, namely, that it is useful to silence it. (c) In general, all men who silence discussion of some opinion do so for some reason which depends upon reference to the opinion the discussion of which they are silencing.

4. People do not have complete liberty of contradicting and disproving an opinion if the discussion of it is silenced.

5. People also do not have complete liberty of contradicting and disproving a belief which depends upon reference to some opinion if the opinion which is referenced by the belief is silenced.

6. We may therefore infer, from #3–5, that whenever a man, or government, silences discussion of some opinion, he does so for some reason which others do not have complete liberty of contradicting and disproving. But to act in this way is to do what was described by #2 as incompatible with acknowledgment of his own fallibility. Therefore, from all the preceding statements, we may conclude that whenever a man, or government, silences discussion of some opinion, he denies his own fallibility, and therefore acts irrationally. Which is to say, it is never rational for a man, or government, to silence discussion of some opinion.

Textual support for the premises

Support for statement #1:

Unfortunately for the good sense of mankind, the fact of their fallibility is far from carrying the weight in their practical judgment, which is always allowed to it in theory; for while every one well knows himself to be fallible, few think it necessary to take any precautions against their own fallibility, or admit the supposition that any opinion, of which they feel very certain, may be one of the examples of the error to which they acknowledge themselves to be liable. (§2¶4)

Support for statement #2:

There is the greatest difference between presuming an opinion to be true, because, with every opportunity for contesting it, it has not been refuted, and assuming its truth for the purpose of not permitting its refutation. Complete liberty of contradicting and disproving our opinion, is the very condition which justifies us in assuming its truth for purposes of action; and on no other terms can a being with human faculties have any rational assurance of being right. (§2¶6)

Support for statement #3(a):

First: the opinion which it is attempted to suppress by authority may possibly be true. Those who desire to suppress it, of course deny its truth; but they are not infallible. They have no authority to decide the question for all mankind, and exclude every other person from the means of judging. To refuse a hearing to an opinion, because they are sure that it is false, is to assume that their certainty is the same thing as absolute certainty. All silencing of discussion is an assumption of infallibility. Its condemnation may be allowed to rest on this common argument, not the worse for being common. (§2¶3)

Support for statement #3(b), statement 4, and statement 5:

It is also often argued, and still oftener thought, that none but bad men would desire to weaken these salutary beliefs; and there can be nothing wrong, it is thought, in restraining bad men, and prohibiting what only such men would wish to practise. This mode of thinking makes the justification of restraints on discussion not a question of the truth of doctrines, but of their usefulness; and flatters itself by that means to escape the responsibility of claiming to be an infallible judge of opinions. But those who thus satisfy themselves, do not perceive that the assumption of infallibility is merely shifted from one point to another. The usefulness of an opinion is itself matter of opinion: as disputable, as open to discussion, and requiring discussion as much, as the opinion itself. There is the same need of an infallible judge of opinions to decide an opinion to be noxious, as to decide it to be false, unless the opinion condemned has full opportunity of defending itself. And it will not do to say that the heretic may be allowed to maintain the utility or harmlessness of his opinion, though forbidden to maintain its truth. The truth of an opinion is part of its utility. (§2¶10)

There is no textual support for statement #3(c), but I think that it is both implied and required. (Or rather, this is what I thought when I first wrote this, almost two years ago.)

Discussion

Few people said anything in the original group thread. In the poll that I made about which premises people disagreed with, #4 was the most popular to be doubted, which shocked me. As I said in a comment written the day after the thread, “Seriously? #4 should be the least controversial here. It is almost a definition.”

Alexander Brown’s paper

In a different thread – actually written before, in 2020-07-05 – I had expressed my heartfelt disagreement with Alexander Brown’s 2010 paper about the argument. It is supposed to defend Mill’s argument, but it denied premise #5 at the end, which I thought to be important. The result, I thought, weakened the argument and made it make less sense. I quote my summary and comments about it from the time:

Alexander Brown [...] discusses various interpretations of the argument. He concludes that not only is all silencing of discussion an assumption of infallibility, but also, silencing of discussion is a necessary condition for an assumption of infallibility to have been made, in Mill’s sense. He also concludes that such an assumption might be made even if censorship is undertaken without a judgment that the belief being censored is false, but with only a judgment that it is useful to suppress it, as in “Thomas Scanlon’s case of a government that acts against a misanthropic inventor who wishes to broadcast his household recipe for nerve gas on television.” Combining two formulæ given in the paper, it may be defined thus:

To make an assumption of infallibility is to feel sure either

(1) that one is right about the truth or falsity of an opinion or

(2) that one has a moral right to suppress an opinion (because of the utility of suppressing that opinion, or because of some form of democratic mandate, for example)

and to attempt to silence public discussion of that opinion on the basis of that feeling. The first case is called a ‘first-order’ assumption of infallibility, since it stems from a judgment about the belief itself being censored, while the second case is called a ‘second-order’ assumption of infallibility.

[...]

I think Mill’s argument is weakened by the denial, at the end of the paper, of the idea that one cannot judge second-order beliefs about an opinion if the opinion itself is being censored. The textual support for the inclusion of second-order assumptions – the claim that “there is the same need of an infallible judge of opinions to decide an opinion to be noxious, as to decide it to be false, unless the opinion condemned has full opportunity of defending itself” – indicates to me that Mill did hold this idea, and I think the argument does not make sense without it.

Without this idea, the argument does not make sense against a government that makes a “second-order assumption of infallibility” about some belief and does not make any attempt to silence contradiction of the second-order belief, such as one that silences denial of the Holocaust, believing that it is useful to do so, but does not silence discussion about whether it is useful to censor denial of the Holocaust – an example discussed at the end of the paper. The government is then acting upon an opinion which everyone has “complete liberty of contradicting and disproving”, and is therefore justified. Unless they really do not have this liberty if the first-order opinion is being censored, it then follows that one kind of “assumption of infallibility”[, the “second-order” kind,] does not make the mistake of denying human fallibility, which was supposed to be the core of the argument, and the reason for the name.

At the time, I felt strongly enough to also e-mail Alexander Brown about it; understandably, I got no reply.

My opinion about the argument

I still think that the argument, as it stands in my old presentation of it, is valid, and possibly sound. The most contentious premise, of course, is the statement #2, which is Mill’s interpretation of what human fallibility means. I accept it, and the rest of the argument, in a limited sense, as follows.

A belief which is “assumed true for the purposes of action” is almost always a probable judgment, i.e., not fully certain. Such a probable judgment, by its nature, does not represent certain knowledge of its object, and may be improved in that respect. So, I would act against the improvement of my own knowledge if I were to deny to others, who may even possibly have superior knowledge about the matter, the possibility of correcting me about it. Acting in this way would seem to be morally wrong, since knowledge is the perfection of man’s rational nature. I could still have no such qualms, however, about silencing a logically incoherent opinion, since pure reason cannot fail, and it is impossible to practically live as though it could.

I think that Catholics may agree with the entire original argument and still support such venerable Church institutions as the execution of heretics, and the Index of Forbidden Books. This may be done if they interpret the Church’s dogmas as being not “one of [their own] opinions”, as premise #2 requires, but rather one of God’s opinions, which are always infallibly correct, and may be “assumed true for the purposes of action” even if no one may discuss them. The Pope does not irrationally assume his own infallibility, but rather accepts it on faith in God, who cannot lie or make mistakes.

Censorship of all opinions other than dogmas would still remain proscribed by the argument. It is to be noted that the argument is concerned, in any event, with the censorship of opinions, and such as may be acted upon at that, so that it does not seem that the argument could ever be used against the censorship of, say, offensive language, or raunchy fiction. This seems to constitute the bulk of censorship, and with the censorship of heresy also excluded, the argument is left with a very limited practical scope.

Human nature

The reader who would form a just estimate of the reasonings of these volumes, cannot perhaps proceed more judiciously, than by examining for himself the truth of these principles, and the support they afford to the various inferences interspersed through the work.

— William Godwin, Enquiry, Summary of Principles

Ethics, as was shown, is supposed to be deduced from human nature. What, then, is human nature?

0. Contents

1. Methodological excursus
2. Postulates
2.1. Rationality and autonomy
2.2. Individual animality
2.2.1. Senses
2.2.2. Sensitive desires
2.2.3. Passions
2.2.4. Vegetative and other powers
2.3. Social animality
2.3.1. Relationships in general
2.3.2. Possible kinds of relationships
2.3.3. Voluntary relationships
2.3.4. Innate relationships, and authority
2.3.5. Human reproduction
2.3.6. Knowledge inequality

1. Methodological excursus

Too many books on ethics leave human nature implicit, simply stating various rights and duties and saying vaguely that they are rooted in human nature. Sometimes they are more specific, but even then, you would have to piece the author’s anthropology from the various rights and duties that he derives from it – much of it never seems to be mentioned outside of ethical demonstrations.

Because of this, the suspicion duly arises that the author is thinking backwards – that he is starting from a certain collection of moral rules that he wants to defend, and then figuring out some reason – often vague or specious – to say that they are natural to mankind after all. Since abduction is forbidden in philosophy, this method would be opposed to philosophy, and would rather constitute poetry.

Sometimes, the authors explicitly use poetry in place of philosophy – that is, they write thought experiments, where they imagine men acting in a supposed ‘state of nature’. Then, if the imaginary experiment seems to show some principle at work, and if the things imagined sound realistic, they think themselves to have found a universal law of nature.

But, of course, imagination is forbidden in philosophy too. A thought experiment could illustrate your conception, but never constitute it.

To avoid all such suspicions, I will make explicit my concept of human nature, as I have understood it from the relevant appearances. In the future, every ethical proposition which I attempt to demonstrate in this blog will be demonstrated through reference to one or more of the principles shown here. No new principles, different from the ones written here, will be introduced as belonging to ‘the human nature’ as a whole. The nature of particular human body parts, however, remains undefined, and I may define it in the future, with new principles peculiar to each part.

One benefit of this is that, if I have made a mistake in my conception, my readers may find this out at the outset, before any ethical demonstrations have been made. I am only one human being, trying my best to observe myself and other human beings, and I may err. That said, I have tried to compose my concept using only what I believe to be very basic, common, and old notions about human nature. They are ones which I believe to be sound, and I take responsibility for the judgment that they belong to human nature; but I also take comfort in my belief that, if I err, I err with mankind. If any of my principles should be disproved, of course, my demonstrations will also be shown to be unsound.

2. Postulates

I accept the traditional idea that man is a rational animal. But I think that this is not an essential definition, which would mean that all rational animals must be men. Human beings, besides being rational, are a particular kind of animals, in ways that I think are metaphysically and ethically relevant.

If there were other rational animals, then, they might not have every single right and duty which I ascribe to human beings.

Nevertheless, even if it is not our specific difference in the logical sense, rationality is still our “highest” and most ethically relevant property, as was shown. It does belong to us by nature in some way.

While I do not dare to attempt a new definition, the following sketch of human nature will exhaust the properties which I find fitting to ascribe to it.

2.1. Rationality and autonomy

Human beings are rational. By this, I mean that they have reason, or intellect. This is the ability, or power, to understand forms, define and divide them, make judgments about them, and deduce conclusions from those judgments. Because of this, human beings have rational desire, which is the desire for knowledge, and therefore for being, generally.

Human beings are also autonomous agents, or free actors, by which I mean that they have free will. As explained before, free will is essentially characterized as the ability to moderate irrational desires and follow rational ones. Without rational desire, and the power to make it apparent, which is the free will, human nature could not be understood as rational.

Since human beings are the only rational parts of the material world, they rightfully have dominion over external things, or property, as was shown.

Following a modern convention, this blog will routinely refer to the human powers of intellect and will as constituting the soul, whereas all other motions will be said to come from the body. This may confuse some traditional metaphysicians; more on this here.

2.2. Individual animality

Human beings are animals, by which I mean only that they are animate and sensitive, having the ability to contain within themselves the efficient and formal causes of their own motions.

This means little without a characterization of human animal powers, which I shall provide next. This section will cover only the human animal powers which I do not immediately find relevant to the consideration of human beings in society, wherefore I titled it “individual”.

2.2.1. Senses

First, human beings have senses, or sensitive powers, which are powers that allow them to perceive appearances. I admit of all the senses that are in common usage.

The external senses include sight, hearing, smell, taste, and touch; the internal senses include the common sense, imagination, the estimative faculty, and sensitive memory. There are other senses, which are not usually as relevant. I mean all of these terms in their common meanings, and I do not find it useful to define them.

2.2.2. Sensitive desires

Second, human beings have sensitive desires, which are desires for sensible things. The power of having sensitive desires is the sensitive appetite, as may be contrasted with the rational appetite, which is the ability to have rational desire.

The sensitive appetite is sometimes distinguished into concupiscible and irascible; the former, also called concupiscence, includes desires to seek what is sensibly pleasant, and to avoid what is unpleasant or painful.

The irascible appetite includes desires to seek what is useful for obtaining something sensibly pleasant, and to avoid what is dangerous because it will lead to something painful; these desires incline us to strive and fight for sensible goods that are difficult to preserve or to attain.

Some typical sensitive desires are hunger, thirst, and sexual desire; other sensitive desires don’t tend to have names, such as the desires for warmth or sleep.

2.2.3. Passions

Third, human beings have passions. While all bodily motions of which human beings are aware, including the senses, may be called passions in a general sense, a narrower sense includes only those motions which are caused by the sensitive appetite, and may also be called emotions. Those passions are sensitive desire itself, pleasure, pain, sorrow, anger, hatred, and compassion. Besides the sensitive desires, which were just explained, I will now define the other passions.

Pleasure is the body’s awareness of the fulfilment of some sensitive desire. Joy, which is the soul’s awareness of the fulfilment of rational desire, is also sometimes called a passion, but this is improper, since it is caused by the rational appetite rather than the sensitive.

Pain and sorrow are the body’s awareness of the appearance of evil. Evil, generally, is a defect in a material thing which makes its appearance more difficult of being understood through its form; in the human being, it is something which would prevent the proper functioning of body parts. Pain is the appearance of evil to the senses, and therefore belongs only to evils afflicting a human being’s own body; sorrow, while also bodily in origin, is caused by a judgment of the intellect regarding some object of sensitive desire.

Hatred, or aversion, is a sensitive desire for something which is opposed to something that is currently apparent, and, therefore, a desire for that apparent thing to disappear. Hence, the proper object of hatred is evil, in the sense just defined.

Anger, properly speaking, differs from hatred in that it is only directed against the perceived injustice of a particular person, and therefore creates a desire that that person be punished.

Compassion, or empathy, is the body’s instinctive awareness, by way of a kind of ‘matching’, of the passions of other animals, including other human beings. This instinct causes a sensitive desire for the apparent good of those animals for which we feel compassion.

I believe that love of other human beings, or of other animals generally, is not completely a passion, but a composite of rational desire for the good of the other, a.k.a. goodwill, and of compassion. This composite is distinct from sexual desire, and completely separable from it; when they exist together, this is what is called “romance”.

Goodwill tends to cause compassion, and, when examined and found to be in accordance with reason, compassion will cause goodwill as well. So it usually makes more sense to speak of love than of either of its components.

2.2.4. Vegetative and other powers

Fourth, and least relevant here, human beings have the so-called vegetative powers, i.e., the powers of metabolism, growth, and reproduction. Since reproduction is very relevant to the consideration of human beings in society, it will be covered in §2.3.5, below.

Human beings also have motor powers; they have arms and legs and such. And they have the power to speak and communicate. As said in the beginning, I intend to define particular human body parts as they become relevant. This sketch only covers what I think belongs to the human being as a whole.

While property in general is derived from the rationality of man, private property, or individual appropriation, exists because of our animal nature. Since human beings have passions and senses, they are not always fully rational; because of this, they may have irreconcilable disagreements about what to do with material objects. Since material objects can not be used for conflicting purposes at the same time, property rights must be assigned, as was shown.

As was also shown, rational assignment of property rights requires the right of self-ownership, which is each human being’s property right over his own body; this will be relevant in later sections.

2.3. Social animality

I will now consider human beings in society, which means, in relationships of various kinds with each other. I will define and divide relationships, and postulate the properties of human nature which create special kinds of relationships.

2.3.1. Relationships in general

By relationship I mean the fact of two human beings seeking the same end ‘coordinately’, i.e., by means of at least one of them being allowed by right, in certain conditions, to control property which the other owns.

2.3.2. Possible kinds of relationships

Accordingly, all possible human relationships may be divided into four kinds, as follows.

According to the end which they seek, relationships may be divided into autotelic and heterotelic. A relationship is autotelic when it seeks the whole good of its constituent persons as its end; it is heterotelic when instead it seeks, as its end, some particular good.

According to their effect upon property, relationships are either equal or unequal. They are equal when the relevant property is owned in common, with no priority between persons; they are unequal when the will of one person has priority over that of the other in decisions about what to do with the property.

These two divisions yield four possible kinds of relationships, viz., the equal autotelic, unequal autotelic, equal heterotelic, and unequal heterotelic.

2.3.3. Voluntary relationships

Voluntary relationships are entered into by the consent of all parties. Since nothing in nature compels anyone to enter any of them, they may exist within any of the four possible kinds.

An equal autotelic voluntary relationship is called a friendship. It is, objectively, the best possible kind of human relationship, since each party receives the greatest benefit that the other can give; it is peculiar to rational animals.

Perfect friendship would occur when two human beings have the same knowledge, which causes them to love each other. Since they have the same knowledge, they have the same plans, so they do not enter into conflicts about what to do with any property. So, between themselves, perfect friends would own all things in common.

Since it is impossible for two human beings to have exactly the same knowledge, there are no perfect friendships in the world. But some relationships approach very nearly to that ideal, so they are called friendships by analogy with that.

An unequal autotelic voluntary relationship is one of voluntary submission. It occurs when two persons love each other, but they recognize that one of them is in some respects wiser and more knowledgeable. The inferior person then agrees, partly for his own good, to submit to the superior’s judgment about those things, and the superior, therefore, effectively controls the inferior’s property regarding them. Since the superior loves the inferior, he will try to teach him what he knows, so that eventually, if conditions are favorable, voluntary submission will become friendship.

An equal heterotelic voluntary relationship, or democratic society, is a relationship entered for a particular purpose, such as business, and in which some property, set apart for the purpose, is put into the common control of all parties. If not all parties involved are perfect friends with each other, this allows for unsolvable conflicts over property to arise, possibly leading to violence. Because of this, democratic societies are contrary to reason, and all heterotelic relationships ought to be unequal.

An unequal heterotelic voluntary relationship, or hierarchical society, is a relationship entered for a particular purpose, such as business, and in which some property, set apart for the purpose, is owned by all parties, but one of them has decision-making priority about it for as long as the relationship lasts. This includes all businesses which are organized hierarchically.

2.3.4. Innate relationships, and authority

Besides voluntary human relationships, there are also innate human relationships, that is, relationships which someone can enter by being born. Those relationships are created by particular properties of human nature which will be explained in the following sections.

In innate relationships, a natural circumstance causes a particular adult person to have control over, love for, and a presumption of superiority in knowledge over, the newborn person. Since this circumstance is created by nature, these things exist by right, and so, the new person is born into an innate kind of unequal autotelic relationship, becoming the inferior of the adult. The adult, becoming his superior, is then said to have authority.

Authority, therefore, gives the superior person the right to, for any good purpose, control the inferior’s property, including the inferior’s body, as well as to be obeyed by the inferior; and it also makes the superior responsible for the inferior’s material welfare and virtuous development.

The inferior is still the owner of his body and property, and although authority may override this for an objectively good purpose, it may not do so for a bad one, which remains an infringement. So, it remains true that no human being is ever the rightful owner of another.

2.3.5. Human reproduction

Reproduction, as it happens in humans, is the source of two natural passions as well as two special kinds of human relationships, marriage and filiation, which together constitute the society called the family.

First, human beings are born particularly helpless, having no knowledge and little physical strength. Parents also have, by nature, especially strong compassion for their children, which property is called the passion of parental love. These natural human properties create the authority of parents over children, and the innate submission of children is called filiation.

Second, human beings reproduce sexually. This is the source of sexual desire, which is a distinct passion, and separable from love. Since sex naturally results in children, it is naturally sought within a voluntary heterotelic relationship, called marriage, which is meant for the purpose of raising the children that result from the sexual act. Since equal heterotelic relationships are contrary to reason, marriage is naturally hierarchical, but nothing in nature makes it necessary that the man, rather than the woman, always be the head of it.

2.3.6. Knowledge inequality

Since human beings are material, and enter the world at different locations in space, they all have different knowledge. Further, some human beings may have a great preponderance, in knowledge, over others. The possibility of such human beings, who may be called sages, or the wise, if actualized, would make it advantageous that all others enter into voluntary submission to them.

Further, it would make it possibly advantageous for God to grant such sages authority over all human beings born in a certain area. This area would be called a state, and the authority of its wise ruler(s) would be called its legitimacy.

It is unclear how precisely God would grant this authority, if he ever did; but it would have to be through some sensible sign that a certain sage, who manifestly has the military means to exercise authority, also has a presumption of superior knowledge over others in the area, and responsibility for them. Nothing other than God could grant this.

After it were given, though, no sensible sign of state authority would have to remain; a legitimate state would, intelligibly, continue to be legitimate until it underwent manifest substantial change.

The human natural property that legitimate states are possible is what I would mean by the traditional phrase that “man is a political animal”. Although political in ancient Greek philosophy referred more to a natural tendency to organize into cities (poleis), in much of modern philosophy it refers to coercive states, which I do believe to be, in certain possible circumstances, compatible with human nature.

I know of no grounds in philosophy or experience to believe that any of the currently existing states are legitimate, or are not. Rationally, non-Catholics may either suspend judgment or take certain facts, such as the apparent beneficial (or not) nature of existing states, as probable indications of their legitimacy (or illegitimacy). Catholics, however, ought to believe on grounds of papal authority that none of the currently existing states are legitimate.

David Hume’s tables

In the old days (one supposes) when the philosopher, labouring by lamp-light in his study, came to this point in his argument, he set down his pen, and looked around for an object in the real world to interrogate. Very commonly that object was the nearest one to hand: his writing-table. ‘Table,’ he said, ‘how do I know that you exist, and, if you do, how do I know that my concept, table, represents your real existence?’ The table would look back without blinking, and interrogate the philosopher in its turn. It was an exacting exchange, and according to which one was the victor in the confrontation, the philosopher would inscribe himself as idealist or a materialist. Or so one must suppose from the frequency with which tables appear.

— E.P. Thompson, The Poverty of Theory

I was much amused by the above quote, which was pointed out to me by a friend. This led me to take notice of the quotations which I shall give below. Together, they support the thesis that, if there really was such a fascination with tables among modern philosophers as E.P. Thompson described, then the works of David Hume must have been a major source for it.

0. Table of contents

1. A Treatise of Human Nature
2. An Abstract of a Book Lately Published
3. A Letter from a Gentleman to His Friend in Edinburgh
4. An Enquiry concerning Human Understanding
5. Other works
6. Appendices

1. A Treatise of Human Nature

In what follows, references will be given by book, part, section, and paragraph, with the paragraph number given separately, since some editions don’t give it. So §1.2.3, ¶4 will refer to Book 1, Part 2, Section 3, paragraph 4. All quotes under this section are from the Treatise, but I will also write “Treatise” into each reference to make it easier to scroll through.

The table before me is alone sufficient by its view to give me the idea of extension. This idea, then, is borrow’d from, and represents some impression, which this moment appears to the senses. But my senses convey to me only the impressions of colour’d points, dispos’d in a certain manner. If the eye is sensible of any thing farther, I desire it may be pointed out to me. But if it be impossible to shew any thing farther, we may conclude with certainty, that the idea of extension is nothing but a copy of these colour’d points, and of the manner of their appearance. (Treatise, §1.2.3, ¶4) 

When [the mind] considers the dye as no longer supported by the box, it can not without violence regard it as suspended in the air; but naturally places it on the table, and views it as turning up one of its sides. (Treatise, §1.3.11, ¶11)

To begin with the question concerning external existence, it may perhaps be said, that setting aside the metaphysical question of the identity of a thinking substance, our own body evidently belongs to us; and as several impressions appear exterior to the body, we suppose them also exterior to ourselves. The paper, on which I write at present, is beyond my hand. The table is beyond the paper. The walls of the chamber beyond the table. And in casting my eye towards the window, I perceive a great extent of fields and buildings beyond my chamber. From all this it may be infer’d, that no other faculty is requir’d, beside the senses, to convince us of the external existence of body. (Treatise, §1.4.2, ¶9)

My bed and table, my books and papers, present themselves in the same uniform manner, and change not upon account of any interruption in my seeing or perceiving them. (Treatise, §1.4.2, ¶18)

’Tis easy to observe, that tho’ bodies are felt by means of their solidity, yet the feeling is a quite different thing from the solidity; and that they have not the least resemblance to each other. A man, who has the palsey in one hand, has as perfect an idea of impenetrability, when he observes that hand to be supported by the table, as when he feels the same table with the other hand. (Treatise, §1.4.4, ¶13)

That table, which just now appears to me, is only a perception, and all its qualities are qualities of a perception. Now the most obvious of all its qualities is extension. The perception consists of parts. These parts are so situated, as to afford us the notion of distance and contiguity; of length, breadth, and thickness. The termination of these three dimensions is what we call figure. (Treatise, §1.4.5, ¶15)

It has been objected to the system of one simple substance in the universe, that this substance being the support or substratum of every thing, must at the very same instant be modify’d into forms, which are contrary and incompatible. The round and square figures are incompatible in the same substance at the same time. How then is it possible, that the same substance can at once be modify’d into that square table, and into this round one? I ask the same question concerning the impressions of these tables; and find that the answer is no more satisfactory in one case than in the other. (Treatise, §1.4.5, ¶25)

When I view this table and that chimney, nothing is present to me but particular perceptions, which are of a like nature with all the other perceptions. This is the doctrine of philosophers. But this table, which is present to me, and that chimney, may and do exist separately. This is the doctrine of the vulgar, and implies no contradiction. There is no contradiction, therefore, in extending the same doctrine to all the perceptions. (Treatise, appendix)

These other passages of the Treatise were not quoted because, while they also mention tables, the mention does not use tables as an example of a perception: §1.4.5, ¶11; §2.1.3, ¶5; §2.1.10, ¶2; §2.2.5, ¶17; §2.3.8, ¶3; §2.3.10, ¶8; §3.2.3, ¶10, note 75. Nevertheless, they show that tables were present to Hume’s mind.

2. An Abstract of a Book Lately Published

In the Abstract, Hume repeats his example of the two billiard balls from the Treatise, §1.3.14, ¶18; but this time he mentions the table that they are on:

Here is a billiard-ball lying on the table, and another ball moving towards it with rapidity. They strike; and the ball, which was formerly at rest, now acquires a motion. [...] I see a billiard-ball moving towards another. I cannot distinguish whether it moves upon its axis, or was struck so as to skim along the table. In the first case, I know it will not stop after the shock. In the second it may stop.

You may count the table as being implied whenever billiard balls are mentioned, if you wish; I have been counting only explicit tables.

3. A Letter from a Gentleman to His Friend in Edinburgh

Speaking of scepticism, Hume wrote this rhetorical question into the Letter:

If I be as much assured of these Principles, as that this Table at which I now write is before me; can any Thing further be desired by the most rigorous Antagonist?

4. An Enquiry concerning Human Understanding

As with the Treatise, I will cite the Enquiry by section and paragraph. I am just calling it Enquiry, since the Moral Enquiry is not as relevant here; see §5 of this blog post for that.

If I see a billiard-ball moving towards another, on a smooth table, I can easily conceive it to stop upon contact. (Enquiry, §5, ¶11)

It seems also evident, that, when men follow this blind and powerful instinct of nature, they always suppose the very images, presented by the senses, to be the external objects, and never entertain any suspicion, that the one are nothing but representations of the other. This very table, which we see white, and which we feel hard, is believed to exist, independent of our perception, and to be something external to our mind, which perceives it. Our presence bestows not being on it: Our absence does not annihilate it. It preserves its existence uniform and entire, independent of the situation of intelligent beings, who perceive or contemplate it.

But this universal and primary opinion of all men is soon destroyed by the slightest philosophy, which teaches us, that nothing can ever be present to the mind but an image or perception, and that the senses are only the inlets, through which these images are conveyed, without being able to produce any immediate intercourse between the mind and the object. The table, which we see, seems to diminish, as we remove farther from it: But the real table, which exists independent of us, suffers no alteration: It was, therefore, nothing but its image, which was present to the mind. These are the obvious dictates of reason; and no man, who reflects, ever doubted, that the existences, which we consider, when we say, this house and that tree, are nothing but perceptions in the mind, and fleeting copies or representations of other existences, which remain uniform and independent. (Enquiry, §12, ¶8–9)

5. Other works

David Hume also mentioned tables in other works, but it was not very relevant to the present subject. For completeness, though, and since this is very easy to do:

• True Account of the Behaviour and Conduct of Archibald Stewart, page 18
• An Enquiry concerning the Principles of Morals, §6, ¶11
• Dissertation on the Passions, §2, ¶31
• History of England, §2, ¶50; §3, ¶51; §5, ¶7; §8, ¶15; §9, ¶10, ¶56; §11, ¶33; §14, ¶35, 39; §16, ¶17; §17, ¶75; §20, ¶11; §21, ¶3, 10; §23, ¶8; §26, ¶37 and the note 23; §31, ¶71; §32, ¶27; §36, ¶30; §37, ¶25; §39, ¶39; §39, ¶86, note 186; §40, ¶4; §44, ¶55, note 98; Appendix 3, ¶60, ¶68; §47, ¶19; Appendix 4, ¶30; §51, ¶65; §52, ¶16, 17, 20, 22; §53, ¶15, 22; §54, ¶38, 44, 72, 87; §59, ¶57; §60, ¶26; §61, ¶62, 63; §62, ¶68; §64, ¶56; §70, ¶60; §71, ¶91.
• Essays: Of Tragedy, ¶4; Of Eloquence, ¶4; Of the Rise and Progress of the Arts and Sciences, ¶40, note 15; Of Polygamy and Divorces, ¶11; Of Simplicity and Refinement in Writing, ¶2; Of Commerce, ¶13; Of Refinement in the Arts, ¶1; Of Money, ¶21.

6. Appendices

Addition from 2023-10-08: One later philosopher who made notable mention of tables was Bertrand Russell, in Chapter 1 of his 1912 book The Problems of Philosophy. David Bostock’s 2012 book Russell’s Logical Atomism, p. 116, describes Russell as holding the “extreme view that I never perceive such things as tables.” [2025-10-12: See also the opening of the introduction to Arthur Eddington’s The Nature of the Physical World, 1928, where he compares his “ordinary table” to his “scientific table”.] [2025-04-26: See also Quine, Word and Object, 1960, which begins, “This familiar desk manifests its presence by resisting my pressures and by deflecting light to my eyes.” Quine doesn’t dwell on the desk, however.]

Addition from 2025-02-20: Tables come up a lot in the metaphysical debate on the existence and ontological status of “ordinary objects”, as this debate is called; see SEP, Ordinary Objects. The book Empty Ideas, by Peter Unger, which uses this debate as a case in point for a general critique of analytic philosophy, also makes extensive mention of tables.

Introduction to natural law ethics

Although all matter is non-being, nevertheless some apparent things can be understood, because, through their appearances, we can understand the forms.

0. Contents

1. Intelligibility differential
2. Application to genera and species
3. Application to individuals
4. Objective value
5. Notes

1. Intelligibility differential

We notice that in some apparent things, the movement is more easily referred to the form than others; the form is, therefore, made more intelligible by those appearances than by others.

Those appearances, being more intelligible, provide us with improved access to form, and therefore to being. Since all being is good, those appearances may be judged to be better – not in respect of themselves, since appearances are not, but in respect of the form which they make more intelligible.

This fact, which I shall call the intelligibility differential, is the only ground of all rational value judgments between appearances.[1]

2. Application to genera and species

The intelligibility differential allows us, first, to judge which kinds of apparent things are better, as follows.

First, animate things are better than inanimate things. This is because animate things, sometimes and to some extent, have within themselves, by their nature,[2] the efficient cause of their own motions. To the extent that this happens, more of their motions can be referred to their form, and therefore they are more intelligible, and so, better.

Second, animate beings that are capable of sensation are better than animate beings which are not capable of sensation. This is because sensitive beings, sometimes and to some extent, have within themselves, by their nature, the formal cause of their own motions – i.e., some appearance which they receive through sense. Their nature determines not only how they move, but also when, and under what conditions. To the extent that this happens, more of their motions can be referred to their form, and therefore they are more intelligible, and so, better.

Third, sensitive beings that are capable of understanding are better than sensitive beings which are not capable of understanding. This is because rational beings, sometimes and to some extent, have within themselves, by their nature, the final cause of their own motions – i.e., some knowledge which they receive through intellect. They are able to seek the ends which their nature determines, not only as they appear, but as they are. To the extent that this happens, more of their motions can be referred to their form, and therefore they are more intelligible, and so, better.

So, to use the Porphyrean definitions, men are better than beasts, and beasts are better than plants, which in turn are better than inanimate things. Nowadays, of course, Porphyry’s assumption that plants are devoid of sensation has been shown to be false. Some people are also trying, with less success, to prove that some of the infrahuman animals have rational powers.

3. Application to individuals

The intelligibility differential allows us, second, to judge which individual apparent things are better, within a certain kind.

This is clear enough – of multiple appearances through which we understand the same form, some of them allow for better understanding of the form. This is because their motions are more conformable to the principles which follow from the form – in other terms, they are more often the cause of their motions than not, and their actions are more in accordance with their last end.[3]

Since more of their motions can be referred to their form, they are more intelligible, and so, better. The best members of a species may be said to be the exemplary ones, the ones that best exemplify the form of the species.

4. Objective value

What it means for any apparent object to be objectively better, metaphysically, has thus been explained. All of the material world could, in principle, be ranked on an objective value scale according to the intelligibility differential; the scale would start from the best human being on earth, then pass through every other human being, then every infrahuman living creature, and then reach the inanimate things, finally stopping at the worst inanimate thing.

A notable special case of this is the case of mankind. Since we are rational, we are able to discover the laws of our nature, i.e., understand the human form, in order to act conformably to it, and therefore become objectively better human beings. The project of doing this is called natural law ethics.[4]

5. Notes

[1] Value judgments are necessarily between things, not about things, since value is ordinal, rather than cardinally quantitative. This is true of both economic value and metaphysical goodness.

[2] The nature of an apparent thing is the form which may be understood through it.

[3] Actions of an object are motions which are efficiently caused by it. Some actions of an object may be referred to its form; this reference, as defined before, is called the final cause. In this context, the form is called the last end.

The motions that are referred to the form, then, are said to be in accordance with, or conformable to, the last end. The motions that are not referred to the form are said to be not in accordance with the last end, or possibly contrary to the last end, if their appearance is judged contrary to the sort of appearance which would be conformable to the end. (Contrary opposition between appearances was defined in §6 of this post.)

[4] The laws of a nature may be defined as the general principles, deduced from our understanding of its form, which govern our judgment that the motions of an apparent thing are, or are not, in accordance with its last end. Natural law may refer, depending on context, to the laws of a specific nature, to the laws of all natures taken together, or to the laws of the human nature in particular.

Substance and accident

I continue my commentary of Hume’s Treatise at the next section, §1.1.6. See my commentary on the previous section here.

0. Contents

1. Origin of substance (¶ 1)
2. Nature of substance (¶ 1–2)
3. Substances and accidents
4. End

1. Origin of substance (¶ 1)

Hume begins the section like this:

I would fain ask those philosophers, who found so much of their reasonings on the distinction of substance and accident, and imagine we have clear ideas of each, whether the idea of substance be derived from the impressions of sensation or of reflection? If it be conveyed to us by our senses, I ask, which of them; and after what manner?

I think I might be one of those philosophers. So I think I should answer Hume’s question.

The concept of substance comes from the fact that we are capable of understanding sensible things.

When we understand a sensible chair, for instance, the object of understanding is, of course, a form, which we might call ‘chairness’. But we also understand various other things about the chair which are not involved in chairness – for instance, it may be a four-footed, wooden chair with a circular back. Since we understand those things, they are also form.

The concept of substance comes by when we understand the chair throughout its undergoing various changes.

We notice that some changes, which are involved in our understanding of chairness, prevent the appearances that we see from being understood through the form of chairness any longer – e.g., if the chair loses its back, we may only be able to understand it as a stool.

Other changes, however, are not involved in our understanding of chairness, and do not prevent our understanding the object as a chair. If the chair somehow loses its woodenness or four-footedness, or the back loses its circularity, we may possibly still understand the resulting object to be a chair – chairness is retained.

In order to distinguish the changes which affect the form by which we understand an object of experience, from those that do not, we come up with the concept of substance. We say that there has been an accidental change when we still understand the object by the same form, and a substantial change when we can no longer do so.

2. Nature of substance (¶ 1–2)

Hume continues:

If it be perceived by the eyes, it must be a colour; if by the ears, a sound; if by the palate, a taste; and so of the other senses. But I believe none will assert, that substance is either a colour, or sound, or a taste. The idea, of substance must therefore be derived from an impression of reflection, if it really exist.

Sure, yeah. Reflection. That sounds like how a concept works, alright.

But the impressions of reflection resolve themselves into our passions and emotions: none of which can possibly represent a substance.

What? Where the hell did he get that idea? Concepts don’t have anything to do with passions and emotions. I hope he explains this later, but I suspect he won’t.

We have therefore no idea of substance, distinct from that of a collection of particular qualities, nor have we any other meaning when we either talk or reason concerning it.

The idea of a substance as well as that of a mode, is nothing but a collection of simple ideas, that are united by the imagination, and have a particular name assigned them, by which we are able to recall, either to ourselves or others, that collection.

This is not quite right, but it is not quite wrong, either. A substance is an appearance through which we can understand a certain form. Since an appearance is a collection of proper sensible qualities – which Hume calls “simple ideas” – it is correct to say that a substance is such a collection given a name, as long as we keep in mind that the name is given because of a form that we understand through the collection.

Accidents, however, are also appearances through which we can understand a certain form, as was said above. So, in what follows, I will distinguish substances from accidents.

3. Substances and accidents

Substances are capable of being imagined by themselves. Accidents can only be imagined as part of the larger collections which we call substances, which is to say, “in a subject”.

So, although the forms which we understand through accidents can be conceived of independently of a subject, they cannot be imagined as existing in this way, which is the same as to say, that they cannot appear without a subject in experience.

This is why Aristotle said that “everything except primary substances is either predicated of primary substances, or is present in them, and if these last did not exist, it would be impossible for anything else to exist.” (Cat., 2b5) Existence here is to be understood as appearance, not being – without substances, there would be no external world, since accidents are incapable of appearing without substances.

Since I have clearly defined substances as a kind of appearance, I do not use Aristotle’s term “secondary substance”. What he called “secondary substances”, I call “forms”.

4. End

I do not find it profitable to give any comments on the rest of ¶2, or on ¶3. I say nothing about modes because, to date, I have never found a use for the term mode when thinking about anything. If I ever wish to talk about modes of anything, I will define the term when I get there.

Hume’s relations

I begin commenting Hume’s Treatise from §1.1.5, because I found the earlier sections less interesting. I will only cite it by section and paragraph number, not page numbers.

0. Contents

1. Terminological note
2. Definition of relation (¶ 1–2)

2.1. My definition

2.2. Hume’s common meaning

2.3. Hume’s philosophical meaning

3. Resemblance (¶ 3)
4. Identity (¶ 4)
5. Space and time; quantity or number; degrees of quality (¶ 5, 6, 7)
6. Contrariety (¶ 8)
7. Cause and effect (¶ 9)
8. Difference (¶ 10)

1. Terminological note

In previous sections of the Treatise, Hume explains his theory of associations of ‘ideas’, which I do not cover here. He says that some associations are made voluntarily, and others are made by “a gentle force, which commonly prevails, and is the cause why, among other things, languages so nearly correspond to each other; nature in a manner pointing out to every one those simple ideas, which are most proper to be united in a complex one.” (§1.1.4, ¶1)

I shall refer to associations that are not made voluntarily as spontaneous. Hume calls them natural, which I must suppose is to be contrasted with artificial. But the will is also part of nature, and more importantly, I think that the term natural association may be ambiguous.

Most importantly, Hume calls them ideas, but says they are in the imagination. I admit of a faculty called the imagination, which is one of the internal senses; but its contents should not be called ideas, since ideas, properly so called, belong to the rational faculty. See, for instance, Poissy on the imagination and on ideas.

I shall assume that Hume is rightly interpreted as speaking about the contents of the imagination, which are properly termed images or phantasms. (I speak of images and phantasms interchangeably, and only use both words to avoid such cacophonous phrases as “images in the imagination”.)

To avoid confusion with Hume’s use of the word idea, I shall refer to ideas, as so called by Poissy, as concepts.

So, I shall only use the word “idea” in direct quotations of Hume, or when paraphrasing his statements. In my own voice, I shall keep images and concepts sharply distinct.

2. Definition of relation (¶ 1–2)

2.1. My definition

Often, to understand an object of experience, reference to a different object is made; this reference is what I shall call relation. To put this in more direct form, relation is a reference to another object which is used as a means to understand an object.

Since this is how I understand the term, I may speak of it as “the proper sense” or “the proper philosophical sense” in what follows, and this is not to be confused with either of the meanings Hume gives to the term.

2.2. Hume’s common meaning

Hume says the word relation has two meanings. The first is “that quality, by which two ideas are connected together in the imagination, and the one naturally introduces the other, after the manner above-explained”, i.e., the cause of the spontaneous association of two images in the imagination. Earlier, he had said that this cause can be either one of exactly three things, viz., resemblance, contiguity in time or place, and causation. Hume says that this first meaning is always the meaning of the word relation “in common language”.

Is it really? I think sometimes it is. In a conversation, I may say two things which someone might find to be unrelated to each other, or something which is unrelated to the topic at hand; in such a case, to explain the relation of the subjects it suffices to say why one reminded me of the other, i.e., the cause of the association of these thoughts in my imagination. I leave aside the question of whether Hume’s division of the causes of mental association is adequate.

In common language, though, now as in his time, relation often refers to family relations, as in the case of brothers or cousins, and I do not see how this is either one of his three causes of association. There are other common senses of the word besides, but I am not as certain that they were current then.

2.3. Hume’s philosophical meaning

The second meaning of relation, which Hume says is only used in philosophy, is “any particular subject of comparison, without a connecting principle.” I suppose “without a connecting principle” means that no cause of spontaneous mental association is required, since the philosophical sense of the word includes even the subjects of comparisons made “upon the arbitrary union of two ideas in the fancy”; in which arbitrary must be taken to mean voluntary, or free.

So, he gives the example of distance as a philosophical relation, since it is a possible subject of voluntary comparison, but cannot be brought under one of his three possible causes of spontaneous association. Accordingly, it is taken in common speech to be something opposed to relation – for “in a common way we say, that nothing can be more distant than such or such things from each other, nothing can have less relation; as if distance and relation were incompatible.” This really is a common way of speech, and if it is admitted that the philosophical sense of relation is foreign to common speech, it would appear to lend support to his division.

I think subjects of comparison, as broadly as Hume thinks of them, are not properly called relations, either commonly or philosophically, and I do not know of any other philosopher who used relation in this sense. Besides, I do not find that Hume’s seven ‘relations’ are all properly called subjects of comparison either. I think he was very confused. Nevertheless, they are interesting subjects to talk about, which is why I’m doing this commentary. If I knew of a more adequate division under which to treat of these things, I would use that division instead of commenting Hume.

3. Resemblance (¶ 3)

Hume speaks of resemblance between phantasms in the imagination, which is a simple bodily experience. Since it is infra-rational, it is not a relation in my sense, and it is not properly a subject of comparison either.

If we consider the senses in analogy to understanding, however, such that seeing is analogous to knowing, then resemblance will be analogous to the understanding of two things through the same universal concept; indeed, things that resemble each other tend usually to be capable of being understood through the same universal concept.

Hume is probably right in thinking that only close resemblances produce spontaneous associations of images. To be sure, though, I would like to see what more recent experimental psychologists have found on the subject.

4. Identity (¶ 4)

Identity, if understood absolutely, is not properly a relation or a subject of comparison, but a transcendental property of being, since everything is identical to itself.

Hume seems to have in mind an object’s capability of being understood to be the same thing before and after some change, though. This happens when the concept by which the object is understood remains the same; it may be called existential identity.

Understood as obtaining between the object before the change and the object after the change, this is not properly a relation, but it is a subject of comparison. To compare two objects in respect of their identity, though, is the same as to compare them in every other possible respect.

5. Space and time; quantity or number; degrees of quality (¶ 5, 6, 7)

These get a section together because Hume was right about calling them subjects of comparison, and they are also the sources of some relations in my own sense of the term. The way in which this happens is somewhat analogous in each case, as well.

Space and time seem to be the sources of some relations in the proper philosophical sense; specifically, the duration or size of one thing may be used as a means to understand the duration or size of another. Thus it was that Aristotle ranked “double”, “half” and “greater” within the category of relation, and gave no other examples of it.

Space and time are also correctly said by Hume to be “the sources of an infinite number of comparisons, such as distant, contiguous, above, below, before, after, &c.”

The numbers of elements in groups of things are also sources of proper relations, as when one number is understood by means of its being greater than, less than, or in some proportion to, another. And they are subjects of comparison as well.

Degrees of qualities are also, similarly, sources of proper relations, as well as subjects of comparison.

It must be noted that, although degrees of proper sensible (a.k.a. secondary) qualities may be ranked ordinally, that is, into more or less intensive, they may not be subject to arithmetical comparisons. There are not, properly, lights that are twice as bright as other lights, or sounds that are twice as loud as other sounds, or colors which correspond to the sum or average of other colors.

All alleged cases of such things are always produced by means of varying common sensible (a.k.a. primary) qualities in the causes that produce the proper sensible qualities. There are, accordingly, different methods of mixing colors, which would be absurd if mixing colors were truly a kind of arithmetical addition.

6. Contrariety (¶ 8)

Hume speaks of contrariety between phantasms in the imagination, which is a simple bodily experience. Since it is infra-rational, it is not a relation in my sense, and it is not properly a subject of comparison either.

Two things are contraries when they cannot be imagined existing in the same place at the same time: as with white and black, fast and slow, square and round.

If we consider the senses in analogy to understanding, such that seeing is analogous to knowing, then contrariety will be analogous to strict contradiction between concepts; indeed, contraries are often understood by contradictory concepts, but this does not always happen.

Contradictory concepts, of which one negates the other, cannot even be conceived of as existing in the same place at the same time; as with white and not-white, fast and not-fast, square and not-square.

Hume says “that no two ideas are in themselves contrary, except those of existence and non-existence”. Actually, we can have no image of “existence”, in general, in our imagination; but to imagine an object existing is just to imagine the object, and to imagine an object not existing is just to imagine something else, in which we then understand that the object does not exist.

Properly, there can be no negation in images, as there can be in concepts, and so, no two images are contradictory to each other, and there can only be a contrary opposition between them. There may be contradiction, however, between the concepts by which we understand the images.

So, many images are in themselves contrary to each other, but no images are contradictory to each other. Since Hume did not keep the relevant terms and faculties distinct enough, he was led to say that “no two ideas are in themselves contrary”, right in the same breath as he called contrariety a relation between ‘ideas’; leaving the reader to wonder why, if they are not contrary in themselves, any ‘ideas’ would be contrary at all. Certainly it is not mere convention which opposes them so.

7. Cause and effect (¶ 9)

Cause and effect is a relation in my sense of the term. In fact, all four kinds of causation are relations, although Hume only included the efficient kind; and they are the most important relations in my sense, being the only ones necessary to all understanding of sensible things.

They are a subject of comparison, insofar as we may compare two things by noting that they had different causes. But to mention that one is the effect of the other is only indirectly a comparison, inasmuch as we know that something cannot be the effect of itself, so that if one thing is the effect of another, the other must have a different cause, which is a difference.

8. Difference (¶ 10)

Hume is right to consider difference “rather as a negation of relation, than as any thing real or positive.”

And it is fair enough to divide difference into “two kinds, as opposed either to identity or resemblance.”

Hume is right to call the negation of identity a difference of number. But the negation of resemblance is not exactly the same as a difference of kind, though it tends to coexist with it.

A difference in kind exists when two images are understood by different concepts. This tends to coincide with the images lacking resemblance in the imagination, but does not always coincide with it, and is at any rate something distinct.

So, to give a proper name to the negation of resemblance, I shall call it a difference of appearance. Accordingly, the other two kinds of difference may be collectively called differences of reality.

On commenting

After I had written the two main divisions of my fundamental metaphysics, I wasn’t sure what to write about next. I chose, in that same post, to divide the four causes, since I tend to use them in many posts, anyway, so it was convenient. But there was no reason to think that that was the most systematically appropriate thing to do at that time. I’m not sure how to organize my thoughts yet.

So my plan, going forward, is to try to comment upon subjects which were treated of in major works on first philosophy. By talking about the same things that they talked about, I would be sure to cover the most important things. If I managed to produce a full commentary of a roughly comprehensive and systematic work, this would assure me of leaving no major topic unexamined.

Since the work would only be used as a guideline for the selection of subjects, though, it is indifferent to me which books to go by. The more classic choice would be to comment upon Aristotle’s Organon and Physics, but I don’t feel like doing that right now. Instead, I have decided to write upon some topics of Hume’s Treatise of Human Nature, which I happened to have been reading recently, and had found very curious and potentially useful for my project.

Commentary has been fruitful for me in the past. When I wrote my review of Moore’s Principia Ethica, it really helped me get my thoughts about ethics in order. I expect that it should be similar with Hume, and whoever else I may decide to comment on in the future.

As a personal note, I think it will probably also be enjoyable. I have always liked giving my comments on what other people have said. Philosophy does begin with dialogue, in my experience; I dearly cherish my best interlocutors.