One of the most helpful recent answers to these questions appears in a collection of essays called Self to Self, by the philosopher J. David Velleman. Velleman denies that there is a single entity that corresponds to all of the ways in which we think and talk about our selves. Instead, the so-called self is really a set of “reflexive guises” that correspond to “at least three distinct selves.” (By “reflexive” he means that the way of thinking in question takes itself as its own subject, as in the sentence “I look at myself,” in which what “I” am looking at is “me.”) The three aspects of selfhood that Velleman has in mind roughly correspond to the sentences above. They are:

A person’s self-image. This is how a person describes who he is and what he stands for. As Velleman puts it, “It is like a photograph in the subject’s mental album, showing just another person but bearing on the reverse side ‘This is me.’” This is the self that prompts us to say things like “That job just didn’t feel like who I am.”

Self-sameness through time. This is “the relation that connects a person to his past and future selves, as they are called.” Velleman believes that such selves are “the past and future persons whom the subject can identify as the ‘I’ of a memory or the ‘I’ of a plan.” This is the self that lets us see ourselves in old VHS tapes of our tenth birthday party.

Autonomous agency. This self is “the agent’s faculty of causal understanding”—the way a person distinguishes between things that are in some sense genuinely his doing and things that are not. Snoring while asleep is not your action in the same way that, for instance, buying tickets to see Iron Maiden because you really enjoy Bruce Dickinson’s singing would be. This self says, “I am doing this because I have this preference.”

As you can see, these are very different functions, and considering them as arising from different aspects of selfhood helps smooth over some of the problems that arise from treating them as unified.