Hume correctly observes that the self is not an object of empirical intuition—we never perceive the 'I' as we perceive objects. But he wrongly concludes that the self is therefore nothing but a bundle of perceptions. The 'I think' must be able to accompany all my representations, or they would not be my representations. This transcendental unity of apperception is not itself an empirical perception; it is the formal condition of all experience. Hume seeks the self among the contents of consciousness, but the self is the unity that synthesizes those contents into a coherent experience. It is not an object of knowledge but the subject that makes knowledge possible. Hume's skepticism about the self results from seeking in experience what can only be established transcendentally.

This is Hume's reductio ad absurdum of the theory of ideas. If we are only ever aware of our perceptions and never of the mind itself, then we cannot know that we exist. But this is manifestly absurd. Every perception necessarily involves a perceiver. To deny the self is to deny the very subject of all our thoughts and experiences. Consciousness is impossible without a conscious subject. When I remember past experiences, I am aware that they are my experiences, experiences of the same self that exists now. This is not a perception among perceptions; it is the necessary presupposition of all perception. Hume's bundle theory is the inevitable consequence of his starting point, but it refutes that starting point by reducing it to absurdity.

Hume's denial of the self is the consequence of his empiricist method applied too ruthlessly. Since we do not have a sensory impression of the self, he concludes it is a fiction. But we know the self more immediately than we know anything else—through direct awareness, not through impression or idea. I am immediately aware of myself as the perceiving subject. This awareness is not mediated by any representation. Hume's mistake is to treat the self as if it should be an object of perception, when in fact it is the subject that does all perceiving. The self is spirit, mind, the active principle that perceives ideas and exercises will. It cannot be reduced to its own perceptions without absurdity.

Hume's analysis is too extreme. While I agree that we do not perceive a metaphysical substance underlying our thoughts, I maintain that personal identity consists in consciousness—specifically, in memory. The self is constituted by the continuity of consciousness over time, by the fact that I remember past experiences as mine. This provides real identity, even if we cannot perceive an unchanging substrate. Hume's bundle theory cannot account for the unity of consciousness, for the fact that it is one mind that has all these diverse perceptions. Memory and the unity of consciousness give us a notion of self that is neither the substantial soul of the scholastics nor the mere bundle of perceptions that Hume describes.

The problem Hume identifies is real but his solution inadequate. There is indeed a difference between numerical identity (strict sameness through time) and what we might call narrative identity (connectedness through memory and similarity). The empirical self—the self as object of inner sense—is indeed a succession of mental states with no unchanging substrate. But this does not exhaust the self. The transcendental self—the 'I' that synthesizes representations into unified consciousness—is not subject to temporal change because it is not in time as objects are. It is the condition for temporal experience, not an object within temporal experience. Hume seeks identity where it cannot be found, among the changing contents of consciousness, while missing the formal unity that makes those contents into one consciousness.

Hume rightly perceives that if we accept his premises, personal identity becomes impossible. A bundle of perceptions that exists only momentarily and then gives way to new perceptions is not a person who persists over time. But instead of rejecting the absurd conclusion, he accepts it and declares personal identity a fiction. This shows the bankruptcy of the theory of ideas. Common sense tells us with certainty that we are the same persons we were yesterday, last year, in childhood. This is not a confusion or fiction; it is a first principle of reason. Hume's skeptical conclusion about the self should lead us to reject his starting point, not to embrace skepticism about our own existence and identity.

Hume's puzzlement about personal identity arises from treating the mind as if it were composed of its ideas rather than being the subject that has those ideas. The mind is a spiritual substance—not the kind of material substance Locke rightly rejected, but an immaterial, thinking, active being. I persist through time because I am a substance, a thing that continues to exist while its ideas change. When my ideas change—when I cease to see red and begin to see blue—there is still one mind that had the first idea and now has the second. This is not fiction but the most certain knowledge we have. The self is known immediately through consciousness, not inferred from perceptions.

Hume here grapples with the problem I raised about the identity of persons over time, but he draws too skeptical a conclusion. I maintained that personal identity consists in continuity of consciousness, particularly memory. The same person is the one who can remember past experiences as their own. Hume is right that there is no unchanging substance underlying our changing thoughts, but wrong to conclude that personal identity is therefore fictitious. Memory provides real continuity and identity even amidst change. When I remember thinking something yesterday, I am aware that it was I who thought it, and this constitutes genuine identity, not mere fiction or confusion.