A rather...odd happenstance happened to me a bit ago. Odd, perhaps, is not the best word, but a lining up of two once-occurring events in a way where they meet, due to timing. It's the internet version of walking down a path you've never taken since it's longer, just to kill 10 extra minutes, then getting hit by lightning due to your travel route. Still, uncommon events still occur, that's what makes them uncommon rather than impossible. Regardless, I digress, the point is that, ignoring the details of the boring but exceedingly unlikely event, it brought to the forefront of my mind something I think about on a semi-regular basis, but have yet to write about -- Identity through time.
Identity through time is one particularly interesting problem to me, particularly since, as a philosopher, my views are far removed from the general populous (Thankfully). However, my views even in the philosophy clique are rather uncommon, making me twice removed. However, before I delve into the vehemently anti-intuition mindset that is my own, I need to explain some things.
This is a complex topic in which you can write a PhD thesis on, so many things will be assumed, ignored, or otherwise not discussed in here. There is the psychology and physiological arguments for identity through time, a ton of variations of those, and many things that otherwise could be explained but won't, however, I'll lay out some of personal beliefs of the best accounts and go on to explain my more general view.
Personal Identity, for me, is in effect a purely psychological occurrence, that is to say physical effects can change personal identity (head wound, for example) but aren't part of it. That is to say, the biological identity of something can be non-changing, while personal identity does. For example: A person who has an accident which damages their mind such that they lose all memories and act differently completely, is still the same biological object, but the personhood has changed such that pre-accident and post-accident people are, in fact, as different as any two random people picked out the globe. Now, there can be a vigorous debate about this, but just assume it's unquestionable, so I can get to my real point.
There is a problem with small changes in a large system, a gradient problem. In essence, it is the ship of Theseus problem. See: http://en.wikipedia.org/wiki/Ship_of_theseus.
Now, gradient problems like this exist in many areas of inquiry, and I can go on a whole tangent about them, but in short, I say this: I reject it as a problem. We either try to define objects into intuitive categories, (which I find inane given the human mind is a sad kludge-together of evolution and the thought intuition and categories that we assign things somehow are a reflection of reality is absurd) or we give in and accept that each change creates something new, so that it doesn't matter how large the leap in the gradient, it is different, and no matter how small, it is different.
What this means, regarding personal identity through time as far as I'm concerned, is that each change no matter how small in effect, creates a new, different, person. Oh, of course, since the changes are in fact so minor that between two seconds we cannot detect any real change, but I'd gladly argue it is there. The changes in, twenty of thirty years, however, might be so vast that if we exclude chronological data, the same biological person is, as far as the mind is concerned, a different person. While the future me rises out of the current me, and as such is likely to be vastly similar, as time goes on each incremental change has the possibility of veering my personally in such a different direction that most similarities could even dissipate through time, albeit the most fundamental traits will probably endure, but still, that's not nearly enough to consider them the same person, otherwise we'd have two strangers being the same person on a regular basis.
So, that is where I get removed from the norm, I consider each chronological movement to, in effect, create a new person. Unintuitive, yes, but I don't see why that's a problem logically. Of course, people can point of problems with this, most if not all I dash with ease, or so I feel... but nonetheless, it is an odd position, I'll admit, though by no means I'll admit it is wrong. The fact is, since the two people that exist at the two closest chronological intervals are going to be so vastly similar, there is no reason to treat them any differently. That is, while in reality they are different people, there's no reason to treat them as something else, until we jump larger periods of time where the similarity to the pervious person may not be quite so similar after all. So then, a person I knew in high school may be in some if not many respects similar, he is a new person. The idea of 'catching up' is in essence meeting the new person. Now, under normal circumstances the changes may not be so vast (though in this range, is probably most likely to be larger than normal), but other circumstances can aggravate changes as well. A kid in high school and a war vet may be six years apart, but... as far as personality goes, can be so vastly different. The person you knew exists in the past, a remnant of time, dead infinite times over, only to be reborn based on the world around them, and their deeds. Reincarnation, writ large.
Now, everything prior to this I'll gladly defend (excluding my little bit of mediocre poetic prose) and admit, the next part however is more silly, but I still find it a fun idea to toy around with, in the vein of Berkeley type bullshit philosophy. I won't go on long about it.
Let us take Plank Time: http://en.wikipedia.org/wiki/Plank_time and apply it to my personal identity through time. Using a film analogy we can draw a similar conclusion. Plank time in essence cuts the universe, or at least, the stages of observing it, into absurdly small pieces, but the speed of them in rapid succession creates the illusion of a singular, constant, event. Much like with a movie, separate pictures seen in rapid succession creates the same illusion. So, then, personhood through time is an illusion as much as movement of pictures rapidly creates a scene that has movement. Perhaps time itself, at least how we see it, is the same.