In his article on personal identity, Hume attacks the general ideas, first that we are conscious of having a "self", and, second, that such a self even exists. Hume argues instead that since all ideas must be based on empirical observation, or sense data which he calls "impressions", and since we have no such impression of our self, then this idea is nothing more than an illusion. The argument is at once counter intuitive and difficult to disprove.

Hume characterizes the views of many philosophers on personal identity and makes a number of claims on their part: first, that throughout our lives we are conscious or aware of having a self; second, that this self has two characteristics, identity over time, and simplicity at a particular moment; third, that sense data are the strongest and only proof we have of the self’s existence, and that the more powerful the sense data the more aware they make us of the self; fifth, that these facts about existence are so important, so pervasive, and so obvious, that no further proof is necessary; and, finally, that doubt on this matter would cause us to doubt any or every other belief we might hold.

Hume does not think these views on the self are as obvious as they seem, nor does he think they can be sufficiently supported. His attacks are based primarily on the same foundation the view’s defenders rely on: namely, the information provided by our senses. In other words, Hume believes theat the little evidence provided by these philosophers is exactly what proves them wrong. According to Hume, it must be a single impression, or sense datum, that justifies an idea and makes it a valid one, and, Hume argues, we have no such single impression of what we like to call our "self". Moreover, the notion of having a single impression of the self is an impossibility, a contradiction, for the self is exactly what we use to refer the multitude of impressions we, or our selves, experience. Such an impression of the self would have to last as long as we take the self to last, our entire lives.

Hume argues that if the philosophers’ view is to believed, there is no way of making sense of the myriad of particular perceptions we experience in daily life. These, says Hume, are clearly distinct from one another; in addition, they don’t necessarily require a single agent or self to exist, or be experienced. As a result, there is no answer to the question of what connection these perceptions have to the self, even if it exists.

The perceptions we experience, says Hume, do not indicate a self, but rather they complicate the possibility of perceiving the self, if it exists. In other words, if one seeks an impression of the self, one is constantly distracted by the particular perceptions that he may be experiencing at that moment. On the other hand, when, at times, there are no particular perception interfering with the possible perception of the self, then one is much less likely to believe that the self exists. for example if one sleeping, or dead, and one cannot hear, touch, see, smell, or taste anything, then it can be sait that the self does not exist.

Instead, Hume would like to argue that what we take to be a unified thing, what we understand as a self which is simple and identical at all times, is nothing more than a "bundle of perceptions" (end of page 162). It is only the fact that varying perceptions follow one oanother at such a speed that leads us to the illusion that there is a single self.

One could make a number of defenses against Hume’s attacks. First, one could easily question the underlying assumption that an idea must be substantiated by a single impression. In fact, one could argue that single impressions are never enough to cause an idea. Instead, ideas are very often formed by taking numerous impressions and discovering relations among them. For example, leaving aside the controversial issue of identity, how would Hume say we assign function to an object, if it is not with many impressions? More simply, how does Hume himself make affirmations about things like "bundles of impressions", if that idea is itself necessarily based on two or more impressions. In other words, one cannot have a single impression of something like a succession, a collection, or a bundle if it is not by saying something about a group of sense data.

Second, one could argue that in the cases that Hume cites as examples of when we do not have impressions, the case of sleep and death, are both cases where there is more going on than sense deprivation. In other words, if while awake someone were able to deprive me of my senses one at a time (with a blindfold, earplugs, and their possible equivalents to the other senses), and if I were to remain conscious throughout the process, I don’t think I would suddenly stop believing I existed when I was momentarily without impressions.

Finally, when I have impressions, I am not only aware of what I am experiencing, but also of a certain attitude or belief structure "through" which I see everything, and this sort of background attitude is, first, relatively unchanging, and, second, very much an unchanging part of "me." In other words, Hume says that he finds himself unable to separate his self from his perceptions, and maybe this is so, since I cannot be aware of this attitude unless as I witness it in terms of a perception, but nevertheless it seems to preceed individual sense data.

In conclusion, Hume might just say I am one of those "metaphysicians" whom he cannot reason with, but although his arguments are so counterintuitive that there must be something wrong with them! That may not sound philosophical enough, but I simply don’t agree that we don’t have an impression of the self separate from our other impressions. Everytime I act or perceive, I think I have to impressions: the impression of what I am doing or seeing, and the thought that "I am doing such and such" or "I am seeing so and so".