Identity

or, why I hate the many-worlds interpretation of quantum mechanics.

The last couple of weeks in my philosophy class focused on personal identity. How we can decide what constitutes personal identity in ourselves (beyond just the sense that this is me), and potentially in other people. Started with Locke's suggestion that memory is necessary and sufficient and then ran Locke into trouble with thought experiments and examinations of 'problem cases' of mental disorders (multiple personalities and such). Derek Parfit has suggestions relating to 'psychological continuity' (mind and mental content continue in an unbroken temporal line) and 'psychological connectedness' (mental content largely the same).

Applying that to our Universe, how do we know we're in the same Universe all the way? Well, it's manifest that the things around us aren't changing and by definition, the Universe we live in is our Universe. As long as we don't wander out of our Universe (and how we'd do that is good question), it's always the same one. Now, the many-worlds interpretation suggests that every time a quantum measurement is made (and measurement is VERY broad), every possible outcome is realised in a different Universe. Aside from the sheer multiplicity of Universes that would be generated in the most tiny of intervals, you sort of lose all sense of identity. At every moment, you're fissioning off an infinity of alternative 'selfs' in other Universes, none of which necessarily continue to bear any resemblance to you. None of these selfs preserves and autonomous existence for any imaginable period, so where does this sense of continuity we experience come from? Besides that, there are some (ridiculously unlikely) outcomes of measurements that would have to be realised in some Universe, and that more or less wipes out the meaning of quantum mechanics' probabilistic predictability. Bleah. In the words of Bernstein's Martin (from Candide), "I have but one word - ABSURD!"