Edge.org is running a great series of talks by social scientists, HeadCon. The latest one by experimental philosopher Joshua Knobe is especially very good. There's also a transcript. Here is a quote:

The question is, given that there's no good psychological theories that involve an actual true self, why do people think that there's a true self? These kinds of theories that we're developing about human cognition can explain why, in the absence of any evidence for this kind of strange phenomenon, we would believe in it. So, what is the thing that's making us believe in it? Right now, we're working on this question, we don't know the answer to it, but one thought that we have is that the belief in something like a true self is the application to the self of a more general capacity we have to think of something like essence. So we have the idea of essence and compare our idea of essence to many different things. And then when we apply it to the idea of the self, we get this notion, the notion of the true self. And what we're seeing in the case of judgment of the true self is this kind of byproduct of our general way of thinking about things as having essences.

If we thought about other kinds of cases in which we might apply this notion of essence, we seem to apply this notion of essence using similar kinds of techniques but we wouldn't ever think in these other cases that the essence of something is actually, literally, a part of that thing. So, suppose you were thinking about a band, say, The Rolling Stones. You might have a certain notion that there's something like the essence of the Stones—what the Stones are really about. Then you might have this idea, you know, all the music that they've been doing since the late seventies is just a betrayal. So, the last 30 years of the Stones is just a betrayal of this thing, the essence of the Stones, like, what the Stones really mean—that's what came out in "Exile on Main Street."

But when we think about it, we're not thinking that the essence of the Stones is something like a certain part of the Stones. Say that the Rolling Stones were in front of us, it's not like we could point to a certain part of the band and say, that is its essence. The essence is this normative notion that if you saw their complete works, you could pick out this thing that's what makes them of value.

Now, with human beings we also apply this notion of essence and it seems like the criteria we use to figure out what is your essence are the same criteria we'd use to figure out what's the essence of the band. We look at all the different things you do, then we try to think, what is the most value in all of things that you do? And we think that is your essence. But then when we try to interpret what it is that we've come up with when we do this, we don't think of it in that way that we would naturally think of the essence of a band, or the essence of the United States, or the essence of social psychology. Instead, what we think is that there's actually some thing in you, like the true self module; it's sending signals to other parts that are being overridden. And it's maybe that that gets us into trouble. When we think of this notion of essences, it's almost something like a psychological theory.