One symptom of that malaise can be found in how obtuse, convoluted and difficult to read are many definitions of identity. (2) The reason for that confusion, is that like the philosophers who need haecceity, many people involved in the production and operation of digital identity services persist in talking about identity as if it is a quality that things have.
But you and I don’t have an identity. Not in the way that a horse has hooves or a square has sides. Identity is not that kind of concept. Things don’t really have identity. In fact, if you start to examine it closely, it is not only in the realm of philosophy that identity starts to become a bit counter-intuitive. Physicists have a lot to say about it too and in their hands identity is just plain weird. (3)
Fortunately we don’t have to understand all the logic and mathematics of identity to make an observation that is useful to the more prosaic activities of information technologists.
Identity is about information.
More practically, instead of worrying what it means for something to have an identity, we can start with the observation that whatever causes it, and whatever it means, there is something about the world that means we can use information to determine if things are the same or different – and we call that something identity.
For example, the different pieces of information, ‘2+5′, ’10-3’ and ‘7’ all mean the same thing. They all represent the same quantity. In another context, the different pieces of information, “Mrs Jane Witherspoon”, “John Witherspoon’s wife”, and even “the woman standing over there”, may all identify the same person.
Identity allows different forms of information can refer to the same thing.
Information can also be used to identify difference. Let’s say there are two people. In that case there should be information that is true of each individually and false of the other. So for example is a man, and the other is a woman. One was an author, and the other a nurse. One was named Rudyard Kipling, and the other Florence Nightingale. We can add more bits of information; date of birth, the names of their parents, nationality, and so on. At some point, if they are indeed different people we should have enough information to distinguish each from the other. Moreover, there should be information that can distinguish each from all the other people who were not, are not and never will be either Rudyard Kipling or Florence Nightingale.
Identity allows information to differentiate one thing from all others.