Phil 89: Hume on Identity


Hume calls everything that’s contained in your mind a perception. He thinks these are all made of:

Hume follows a tradition of theorists like Aristotle, Aquinas, Francis Bacon, Newton, and especially Locke, thinking that all the ideas/concepts we have (and all we know using them) have to come from experience. For Hume, this amounts to a requirement that every idea is either copied from some impressions, or else is made by combining, dividing, rearranging other impressions and ideas. This is one important background principle to our reading selection.

Here are two other background principles, which may help you follow Hume’s discussion. Hume has argued elsewhere that we can’t have any ideas/understanding of:

By “external substances,” I mean substances outside your own mind. Hume will be arguing in our reading that you don’t have any idea/understanding of your own mind as a substance, either. (This is a question he focuses on in the reading, not a “background principle.”) So on Hume’s account, there won’t be any substances in the external world nor in your own mind.

Locke, by contrast, thought we did have ideas of substances: these ideas were just incomplete and obscure in some ways. And how Locke thought of the relation between selves/persons and substances isn’t entirely clear.

Regarding “necessary connections,” Hume ends up proposing a radical alternative account of what we mean when we think about causation. There are controversies about how exactly to understand him; but for the purposes of our reading, we don’t need to track all that. I’m just identifying this as part of the background so you understand why Hume says things like:

if we would recollect what has been already proved at large, that the understanding never observes any real connexion among objects (p. 169)

Chapter 12 is from an appendix that Hume published a year or so after the previous chapters. There he summarizes what he takes himself to have attempted in those chapters, and ends by expressing some dissatisfaction about parts of his account. It’s not entirely clear what Hume’s reservations were, but they appear connected to his views about causation. We won’t try to sort that out. The main thing for us to look for in Chapter 12 is how Hume describes what he’s trying to do in Chapter 11.


Hume uses some unfamiliar words, and uses other words in ways that differ from how they’re usually understood nowadays. For example, I’ve already mentioned that he uses “perceptions” in a broader sense that contemporary philosophers do. Here are some more examples:

Identity for External Objects

I said that one background principle to our reading is that every idea is either copied from some impressions, or derived by operations on other impressions and ideas.

When Hume asks at the start of Chapter 10, “What is the principle of individuation?” he is asking what impression might be the source of our idea of identity.

That chapter raises a puzzle about finding any such impression, since if we experience only one object we seem only to get an idea of oneness (what Hume calls “unity”), but that’s not yet an idea of anything being identical to anything. On the other hand if we experience more than one object we get an idea of manyness or plurality (what Hume calls “number”), but again that’s not an idea of identity, since many things aren’t identical. Hume comes up with an answer that satisfies him, by saying we get our idea of identity by experiencing one object for a length of time during which the object doesn’t change in any way. So he concludes that’s what our idea of identity has to mean. If we ever talk about some earlier object being identical to a later version of the same object, we have to mean that the object hasn’t changed. This makes it sound like Hume might not be distinguishing between numerical and qualitative identity. But he does acknowledge that distinction: see p. 167, where he calls qualitative identity “specific identity.”

Hume’s discussion in Chapter 11 then diagnoses why we often “attribute” or talk about identity when things have changed.

We don’t have to buy into Hume’s starting assumptions. In his summary, Perry complains:

The search for an impression of identity is unnecessary, the problem produced when one is not found, illusory, and the impression Hume finally comes up with, irrelevant. (p. 28)

But to understand Hume’s discussion, it is important to appreciate that this is his starting point.

Hume repeats his account of our idea of identity in Chapter 11:

We have a distinct idea of an object, that remains invariable and uninterrupted through a supposed variation of time; and this idea we call that of identity or sameness. We have also a distinct idea of several different objects existing in succession, and connected together by a close relation; and this to an accurate view affords as perfect a notion of diversity, as if there was no manner of relation among the objects. But though these two ideas of identity, and a succession of related objects be in themselves perfectly distinct, and even contrary, yet ’tis certain, that in our common way of thinking they are generally confounded with each other. (p. 163)

On Hume’s picture, it will only be “proper” to speak of identity when the object is “uninterrupted” and “invariable” (unchanging) (p. 164-5). We do in fact attribute identity to other objects, but this is a “confusion and mistake” (p. 164). All that is really there is a “succession” or changing sequence of different objects (p 163-5).

Hume proceeds to discuss how it happens that we “confound” our ideas of a single object remaining identical and unchanged and of a succession/changing sequence of different objects. He says:

That action of the imagination, by which we consider the uninterrupted and invariable object, and that by which we reflect on the succession of related objects, are almost the same to the feeling, nor is there much more effort of thought required in the latter case than in the former. The relation facilitates the transition of the mind from one object to another, and renders its passage as smooth as if it contemplated one continued object. This resemblance is the cause of the confusion and mistake, and makes us substitute the notion of identity, instead of that of related objects. (p. 163-4)

He’s saying that when we look at or imagine a succession of different/changing objects, it can sometimes feel similar to a situation where we’re only looking at a single “invariable” object. But he’ll argue that these situations only feel similar:

[T]he objects, which are variable or interrupted, and yet are supposed to continue the same, are such only as consist of a succession of parts, connected together by resemblance, contiguity, or causation. These are the “close relations” Hume mentioned in a previous passage. For as such a succession answers evidently to our notion of diversity, it can only be by mistake we ascribe to it an identity; and as the relation of parts, which leads us into this mistake, is really nothing but a quality, which produces an association of ideas, and an easy transition of the imagination from one to another, it can only be from the resemblance, which this act of the mind bears to that, by which we contemplate one continued object, that the error arises… [A]ll objects, to which we ascribe identity, without observing their invariableness and uninterruptedness, are such as consist of a succession of related objects. (p. 165)

Let’s agree with Hume that these situations can sometimes feel similar: see this video for a nice example. Hume offers a number of explanations for how this can happen: for example if only a small part is added or removed, or the object changes very gradually (p. 165-8). But for a number of examples he discusses, like:

it’s hard to believe that we’re making the mistake Hume imagines. When we do realize an object is changing, but still want to attribute identity to it, Hume says we make a “fiction” of some persisting invariable element like a substance that “connects” and “unifies” all the other varying parts and qualities (p. 164-5, 171-2).

Hume on Personal Identity

Hume is not the first philosopher to raise doubts about external substances; but he is the first to push this picture also to selves/persons. What he opposes are views that say the self is something simple that remains “strictly and properly” identical to itself over time, like a soul (or any other substance). Instead, he’ll argue we can only understand our self as a succession of “perceptions” that are connected by memory and other relations.

Here are some passages where Hume states his own picture:

The identity, which we ascribe to the mind of man, is only a fictitious one, and of a like kind with that which we ascribe to vegetables and animal bodies. (p. 168)

Philosophers begin to be reconciled to the principle, that we have no idea of external substance, distinct from the ideas of particular qualities. This must pave the way for a like principle with regard to the mind, that we have no notion of it, distinct from the particular perceptions. (p. 175)

[We] are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in perpetual flux and movement… There is properly no simplicity in [the mind] at one time, nor identity in different, whatever natural propension we may have to imagine that simplicity and identity. (p. 162-3)

I cannot compare the [self] more properly to any tjing than to a republic or commonwealth, in which the several members are united by the reciprocal laws of government and subordination, and give rise to other persons who propagate tje same republic in the incessant changes of its parts. And as the same individual republic may not only change its members, but also its laws and constitutions; in like manner the same person may vary his character and disposition, as well as his impressions and ideas, without losing his identity. Whatever changes he endures, his several parts are still connected by the relation of causation. (p. 170)

For my part, when I enter most intimately into what I call myself that is, when I introspectively reflect on what’s present to my mind, I always stumble upon some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe any thing but the perception. When my perceptions are removed for any time, as by sound sleep, so long am I insensible of myself, and may truly be said not to exist… If any one, upon serious and unprejudiced reflection, thinks he has a different notion of himself, I must confess I can reason no longer with him… He may, perhaps, perceive something simple and continued, which he calls himself, though I am certain there is no such [thing to be perceived] in me. (p. 162)

When I turn my reflection on myself, I never can perceive this self without some one or more perceptions; nor can I ever perceive any thing but the perceptions. ’Tis the composition of these, therefore, which forms the self. (p. 174)

We can conceive a thinking being to have either many or few perceptions. Suppose the mind to be reduced even below the life of an oyster. Suppose it to have only one perception, as of thirst or hunger. Consider it in that situation. Do you conceive any thing but merely that perception? Have you any notion of self or substance? If not, the addition of other perceptions can never give you that notion. (p. 174)

The annihilation, which some people suppose to follow upon death, and which entirely destroys this self, is nothing but an extinction of all particular perceptions; love and hatred, pain and pleasure, thought and sensation. These therefore must be the same with self; since the one cannot survive the other. (p. 174-5, see also p. 162)

Hume’s picture of the self sounds a lot like Locke’s. There are some difference, though.

A final difference is more subtle and complex. One thing that’s clear about Locke is that he thinks selves/persons really exist. There’s scholarly dispute about what sort of things Locke thinks persons are: are they a new sort of substance? or something else? But whatever they are, it’s clear that Locke thinks they are real.

By contrast, this is less clear with Hume.

Are Selves an Illusion?

Part of the problem here has to do with Hume’s background views on causation. He writes in Chapter 12:

If perceptions are distinct existences, they form a whole only by being connected together. But no connexions among distinct existences are ever discoverable by human understanding. We only feel a connexion or determination of the thought, to pass from one object to another… [W]hen reflecting on the train of past perceptions, that compose a mind, the ideas of them are felt to be connected together, and naturally introduce each other. (p. 175)

On Hume’s account, what makes the events in a mind count as a single “self” are largely the causal relations between them. But on his official account of causation, there are no real causal relations in the phenomena themselves — in fact, we can’t even understand what those could be. This is true even when the phenomena are elements of our own mind. This tension drives the reservations Hume voices at the end of Chapter 12.

Because of this tension, some readers take Hume to be arguing that the self is an illusion. It’s not just that the self is not a substance, but might be something else like Locke envisaged. Rather, there is no self.

Perry reads Hume this way, and so did Hume’s contemporaries like Reid. Here’s a passage that might support this reading:

’Tis still true, that every distinct perception, which enters into the composition of the mind, is a distinct existence, and is different, and distinguishable, and separable from every other perception, either contemporary or successive. But, as, notwithstanding this distinction and separability, we suppose the whole train of perceptions to be united by identity, a question naturally arises concerning this relation of identity, whether it be something that really binds our several perceptions together, or only associates their ideas in the imagination. That is, in other words, whether in pronouncing concerning the identity of a person, we observe some real bond among his perceptions, or only feel one among the ideas we form of them. This question we might easily decide, if we would recollect what has been already proved at large, that the understanding never observes any real connexion among objects… [I]dentity is nothing really belonging to these different perceptions, and uniting them together, but is merely a quality, which we attribute to them, because of the union of their ideas in the imagination, when we reflect upon them… [O]ur notions of personal identity, proceed entirely from the smooth and uninterrupted progress of the thought along a train of connected ideas… (p. 168-9, my underlining)

Perry thinks that Hume should instead have said that the collection of perceptions he discusses is the self:

I believe Hume offers an interesting if sketchy theory Perry means the details aren’t filled in of personal identity, a causal theory, disguised as the revolutionary discovery that there is no such thing as personal identity. (p. 26)

On a competing reading of Hume, Hume does hold something like the view Perry says he ought to hold. He doesn’t think our selves are an illusion. Instead, all thinks is illusory is a certain picture of the self, held by his opponents: of something simple and and “strictly identical” to itself over time. Hume is arguing that there is no self of that sort. But he’d agree with Perry that some collection of perceptions can correctly be called “me, myself.” On this reading, Hume will agree with Locke that selves/persons do really exist. (But he’d continue to deny that a self remains identical over time, according to the way he “strictly” understands that.)

This second reading seems to me somewhat better supported by careful attention to our readings. Note the parts I’ve underlined in these passages:

There are some philosophers, who imagine we are every moment intimately conscious of what we call our self, that we feel its existence and its continuance in existence; and are certain, beyond the evidence of a demonstration, both of its perfect identity and simplicity… Unluckily all these positive assertions are contrary to that very experience which is pleaded for them, nor have we any idea of self, after the manner it is here explained. For, from what impression could this idea be derived?… [S]elf or person is not any one impression, but that to which our several impressions and ideas are supposed to [be related]. If any impression gives rise to the idea of self, that impression must continue invariably the same, through the whole course of our lives, since self is supposed to exist after that manner. But there is no impression constant and invariable… It cannot therefore be from any of these impressions, or from any other, that the idea of self is derived, and consequently there is no such idea. (pp. 161-2)

When we talk of self or substance, we must have an idea annexed to these terms, otherwise they are altogether unintelligible. Every idea is derived from preceding impressions; and we have no impression of self or substance, as something simple and individual. We have, therefore, no idea of them in that sense. (p. 173)

Some Questions about Persons Have no Definite and Objective Answer?

We’ve seen Williams arguing that questions of personal identity, unlike questions of identity for ships and trees and rivers, must always have a definite yes or no answer, that isn’t settled by our linguistic conventions. I said that some authors we went on to look at would disagree. Hume is one of these authors:

The whole of this doctrine leads us to a conclusion, which is of great importance in the present affair, viz. that all the nice and subtle questions concerning personal identity can never possibly be decided, and are to be regarded rather as grammatical than as philosophical difficulties… [A]s the relations [on which identity depends], and the easiness of [our mind’s] transition may diminish by insensible degrees, we have no just standard, by which we can decide any dispute concerning the time, when they acquire or lose a title to the name of identity. All the disputes concerning the identity of connected objects are merely verbal, except so far as the relation of parts gives rise to some fiction or imaginary principle of union, as we have already observed. (p. 171)

In coming classes we’ll be reading Parfit who’s another.