The first can be called the concept of plain identity. This is the concept of identity understood in the most unrestrictive way, that is, when ‘identity’ is understood to mean simply ‘that which a person can be identified as’. On this concept of identity, as long as something is true of a person, we can refer to it as one of her identities. The concept of plain identity is so unrestrictive that a plain identity of a person does not even have to be something that the person can be uniquely identified as. I have, for instance, the unique identity as my son’s father, but I also have the identity as a father, which is not unique. This feature of plain identity accords well with our everyday use of the word ‘identity’, such as when we speak of our cultural, social, national, or professional identities and when we speak of different people’s having the same identity.
It is clear that in this unrestrictive sense of identity I can have many identities; some of them cover a large set of my activities and a long period of time, while others cover just a particular involvement at a particular time. One of my plain identities is a professor of philosophy, which is a long-term identity that involves doing different kinds of things; it is also one of my plain identities that I am the person who is writing this very sentence that I am now writing, and this is one single activity that lasts only for a very short while. Not only activities or projects that I positively undertake form my plain identities, things that are entirely not up to me, or not entirely up to me, also form my plain identities.
The second concept of identity can be called the concept of self-identity. A person’s plain identity becomes his self-identity if he identifies himself, or self-identifies, with that identity --- if he sees the identity as defining who he is, or at least part of who he is. In one of its usages, the term ‘self’ refers precisely to self-identity as I define it here. In this usage, as David Velleman points out, “the term ‘self’ refers --- not to the person, or a part of the person, represented reflexively --- but to the person’s own reflexive representations, which make up his self-image or self-conception” and which gives him “his sense of who he is” (Velleman, Self to Self, pp.355-356).
It is obvious that not every one of my plain identities is what I would consider to be part of who I am, or constitutes part of my self-image or self-conception. It is, for example, a plain identity of mine that I am the person who is typing this very sentence that I am now typing, but I certainly do not think this identity is part of who I am. Indeed, even when a plain identity of mine is considered by others to be who I am because it is, as they see it, an important identity, I may not agree with them. If I myself do not consider the plain identity as part of who I am, then it is not my self-identity. As Bernard Williams puts it, “[t]he difference between an identity which is mine and which I eagerly recognize as mine, and an identity as what someone else simply assumes me to be, is in one sense all the difference in the world” (Williams, Philosophy as a Humanistic Discipline, p.62).
Williams’s remark seems to suggest that if I self-identify with a plain identity of mine, it must be a plain identity that I value, that is, something that I want myself to be or something that I think I should be rather than merely something that I admit I actually am. Given that most people have the natural tendency to see themselves positively and have the psychological need for self-esteem, people normally value their self-identities. This may be why some philosophers understand self-identity in terms of reflective endorsement: what it is for a person to identify herself with her identity is for her to approve of it after reflecting on whether she should approve of it.
However, given the complexity of human psychology, as exemplified by phenomena like self-hatred and despising oneself, it does not seem difficult to imagine a person who self-identifies with an identity that she disvalues. If I were a Dalit (an untouchable) in India, I might, because of how I was brought up and because of how the caste system works, self-identify with my identity as a Dalit and see myself as being obligated by that identity to act in particular ways, but I did not have to value that identity (why should I?). In any case, I certainly can identify myself with an identity that I do not value or disvalue ¾ not everything that I admit as defining who I am is also something that I am proud of being, something that I see as good in some way, something that I think I should be.
The third concept of identity, which is closely relation to the concept of self-identity and also what we need for evaluating a biographical life, can be called the concept of unifying-identity. A unifying-identity is a self-identity that unifies different parts of a person’s biographical life into a narrative whole that can easily develop further by virtue of that very self-identity (if the person continues to live). Since a unifying-identity unifies different parts of a person’s life, it contains many plain identities of that person, some of which may be that person’s self-identities. A unifying-identity must itself be a self-identity, but a self-identity is not necessarily a unifying-identity, just as a self-identity must itself be a plain identity, but a plain identity is not necessarily a self-identity. A self-identity that is not a unifying-identity may still form a narrative whole in the sense that it constitutes a story that has a beginning and an end; the reason why it is not a unifying-identity is that the narrative whole cannot easily develop further by virtue of that self-identity. Since a self-identity can be a unifying-identity, if some of the self-identities contained in a unifying-identity are themselves unifying-identities, it will be a case of a unifying-identity containing other unifying-identities as its parts.
The distinction between self-identity and unifying-identity is not clear-cut, that is, it is sometimes difficult to tell whether a self-identity is also a unifying-identity. But it is not hard to see that there is a distinction when what we consider is not a borderline case.