For those of you that are not fans of Only Fools and Horses, the title of this post is a reference to Trigger's broom. This is the episode where he receives an award for using the same broom for 20 years, only to reveal later that it has been replaced entirely several times. Of course, when I first saw that episode I never realized that Trigger's broom raises an interesting paradox. More specifically Theseus' Paradox, which asks the question whether it is the same object once the majority of it has been replaced.
One can apply various arguments about the intent of the object to get around this paradox, but I wonder how this applies to people. So I can think of two ways in which we can apply this to a person. First, actual replacement of body parts. Putting the medical difficulties aside, if we could do a brain transplant would the new person be the same as the one that owned the brain or is this an altogether new person? I guess we could say that it is the person's personality which defines who they are, not necessarily their look. That is, people would eventually get over the completely new body and face, once they realize it is the "same" person inside.
Let's now look at the second way of applying this paradox to people: their personalities. Now imagine a person, and it does happen, completely/significantly changing their personality. So is there any truth in when someone turns around and says "you are not the same person any more"? What I find interesting is this idea of some kind of defining characteristic. Once that is gone, then we are no longer the same person. You might take a couple of different positions at this point. You might say that the sum of our personality is what defines us; or you might take the position that there are certain aspects of us that are unique and define us. We could conduct a thought experiment by which we swap aspects someone's personalities in small steps. I shall not go into too much detail here, but the basic idea is that through a series of logical arguments we can swap these personality aspects without anyone objecting or questioning the identity of the person in question. So what is it that defines us? I believe it is everything (individually and as a whole), because if you can swap one aspect of you without changing anything then you can swap everything. So even the smallest component of our personality is a defining and crucial component.
Of course, in all of the above there is major aspect of how others define us. I will have to leave an in-depth discussion of this topic for another post, but it seems to me that our identities are by no means solely based on our definitions of them. Instead, how others view us appears to play an important role in our defining characteristics. It's a shame --- it takes years to be happy with ourselves!
