Personal Identity: Who are you? What am I?

Posted on September 26, 2012 by

Here, I’ll be discussing the problem of personal identity. My aim is to offer a brief historical account of the problem touching briefly on bodily identity followed by Hume’s take on it. ‘Psychological continuity theories’ (PCT) are most popular (Parfit, Noonan, etc.) but I won’t discuss the details of them in this post (maybe future posts). Rather, I’d like to touch on Hume’s view and offer some reasons for thinking it can be described as a PCT view. I won’t have a robust view worked out, not yet anyway, as my main purposes here are to generate some discussion as to what readers think about the concept after getting a brief run-down/refresher as to what the problem entails. First, to get started, why should anyone (including non-philosophers) care about personal identity? Here, an answer by Harold Noonan, in his book “Personal Identity”(2003 Routledge) is spot on when  he says;

Man has always hoped to survive his bodily death, and it is a central tenet of many religions that such survival is possible, and what forms, if any, it might take, are matters which depend crucially on the nature of personal identity over time. For to survive, in the sense that concerns us, means to continue to exist as persons identifiable as those here and now

For me, the intimate connection between personal identity (PI) on the one hand and the concept of moral responsibility for past actions and practices of praise and blame on the other has forced me to wrestle with what it means to be a person as a continuing entity through time. If we suddenly gave up on the notion of personal identity, or, if we were to fail to give a plausible account of it, we would be hard-pressed to justify both our moral and emotional responses to persons committing unethical acts against us or others. So, let’s first discuss what history has to tell us about the concept of identity before moving to the specific views.

What do we mean when we refer to the “I” when we make claims about ourselves? Not to sound cliche but the concept of personal identity has baffled philosophers for centuries. All theories of personal identity seem to have their short-falls, yet, we have no trouble claiming the “we” exist in some enduring way. But what is it about us that endures over time?


The Philosophical term ‘identity’ is a relational term, specifically, a relation that x and y stand in, just in case they are the same thing, or identical to each other. For instance, the claim that a book at time t1 is the same book at time t1+1 is an identity claim. Metaphysical questions surrounding identity are broad and vexing. For instance, what does it mean for an object to be the same as itself? If an object does change (even slightly) what does it mean for that object, person or not, to be the same? Philosopher/Mathematician Gottfried Leibniz has a way of dealing with such questions. Leibniz Law, as it is referred to, claims that  “x is the same as y if and only if every predicate true of x is true of y as well.”

This all seems pretty straight-forward, right? So where lies the problem? Well, many of the things that we refer to on a day-to-day basis (even minute to minute) are changing (some changes are obvious while most are so slight that we don’t even recognize them). Our environment is always changing and these changes affect the object of reference. Think of the example of the book again. If I tear a page, is it the same book? If I tear half the pages, same book? How about if I white out the pages and write new words on every page, same book? The questions are endless. Identity claims seem to fall prey to the problem of vagueness, but, rather than focus on the problem I’d like to turn to some possible answers. In light of what has been said thus far regarding the book example, what would it mean for any of ‘us’ to have an identity? First, I’ll mention the initial arguments that one might have before moving on to David Hume. Keep in mind that this is a gross generalization.


Probably the most intuitive view, but the least popular with philosophers (at least the generic understanding of it). Bodily identity is the claim that personal identity is no different from identity of other objects, like a book. This view conforms to our ordinary usage of identity terms and makes sense, prima facie, but is has some glaring problems.

Earlier, when referencing the book I asked a series of questions. Tear a page, same book? Tear a chapter, same book? Etc. The point there was to put some pressure on when in fact the book would cease to exist, we can do the same with bodily identity. If you lost an arm, are you still you? What about all your limbs? How about all your organs? How about everything? At what point is it not you? How about if I remove your brain and place it into someone else’s body, are you still you or does your change in body change who you are? If you think that the person that has your brain but a completely different body is you then you must reject the bodily identity theory in favor of a more specific, brain criterion theory (we’ll get back to the brain theory in subsequent posts). Any way you cut it the brain is of crucial importance when thinking about personal identity, it seems much more important than the body, as a whole. Regardless of its shortfalls this is one way to cash out the notion of personal identity.


Hume actually rejects the notion of personal identity over time, however, I’ll pose his theory as one that could be taken as a version of a memory theory.

Hume says that all that “we” are is a bundle of perceptions at any given reference point. The ‘self’ for Hume, when perceived as something fixed through time, is an illusion. Strict identity claims are simply false when talking about ourselves as persisting through time.The bundle of perceptions changes with each experience, therefore, there is no one enduring ‘self’ that persists through each experience.

Hume thinks that the ‘self’ as a concept that persists through time is an illusion.

So, what we identify as ourselves at any one point in time is different from any other point in time because the bundle has changed. The new experience or impressions have necessarily changed the bundle from its previous state. Think of the bundle of perceptions as a pile of bricks. Once we add another brick to the pile the pile has changed. Necessarily, this means that the pile is not the same. And, since identity relations are, according to Hume, strict claims (following Leibnitz’s Law), then we are not warranted in calling ourselves the same at any two points in time. So, the Justin that’s writing this post is different from the Justin that walked into the office this morning. Strictly speaking, I’m not the same guy that walked into the room a few hours ago. Initially, I wanted to reject this view out of hand. How could it be that I am not the same as I was a few hours ago? Sure, changes occur, but I’m no longer Justin? The notion seemed ridiculous! But, if it is, why? Well, Hume gives us some good motivation for thinking this way about ourselves. First, our minds, according to Hume, readily pass from one thing to another. When things resemble one another we automatically relate them with use of our imagination. This is why we call a door a door even though we may never have seen that particular door which we are referring to. Hume gives us a much deeper story than this, but, again, I’m purposely being quick and fast here. So, because I resemble my past ‘self’ of a few hours ago, I quickly move to the claim that I am the same person that entered the office. But, if we think long and hard about who we are or what we are it seems that Hume might be right (there are many responses one could give here). Are we not a collection or a bundle of perceptions at any given time? Sure, his initial claim that we are not the same at any two points doesn’t seem intuitive, but, that aside, it sure seems right. If we are not a bundle or collection of perceptions then what are we? This bundle will surely include our memories of our past  and the current perceptions I am taking in now. It seems like a linguistic convention to call Justin, Justin, at any given time. And that’s fine with me, but strictly speaking, I am not the same. So, what can we mean when we make a claim about ourselves?

When I say “I will go home in an hour” I’m referring to the bundle of perceptions that is related by past experiences to the bundle that will walk out the door. I may be wrong in my claim that ‘I’ will leave in an hour (I may take longer or turn in sooner, but, I will leave at some point),  the ‘I’ is simply a quick and fast way of identifying who will walk out the door. My wife is different than me, this seems obvious. I can’t claim that it will be her that walks out the door because she does not have the same relation to the bundle walking out the door as I will when ‘I’ make the move. So, personal identity is then a detailed relation between one bundle and another. That relation must be a continuous one from one bundle to the next. And, though strictly speaking, I am not “identical” to the bundle of 5 minutes ago, a view such as this can still account for the “I” by relations between bundles connected through memory. One need not have a fixed memory or even a good one to be a person or a self on this account. This gets us around those who have Alzheimer’s. They are still persons on this view. And, it might get around some of the issues related to memory as we’ll see in later posts. But, let’s look at some problems and questions that arise for this view.

Is our bundle of perceptions every perception we have ever had? I don’t remember some things, did those things that I have forgotten not play any role in who I am today? And, if I don’t remember something how can it actually be in my bundle? Surely my past actions play some sort of role in how I perceive a particular situation, but how can this theory account for those experiences  being “our own”. For instance, we have no recollection of our childhood ages of 0-5 (at least I don’t), but surely, as psychological research has pointed out, these years are crucial to our development. The things we learned in the past surely affected the person we were at 12 and the person at 12 surely affected the person we were at 18, and so on.

I don’t necessarily think this is the best view of identity but it seems plausible. Parfit has an intriguing view as well, but, I’ll save that for a later post. I should also mention that I am not endorsing this Humean view, I’m just toying with it a bit.