I'm doing a Summer Semester at Uni on Greek Philosophy. So far I'm finding it quite enjoyable. Today we looked at Parmenides and I experienced the same blissful confusion that I experienced when I first read Descartes. It's a strange feeling, when the conclusion seems bizarre and you're sure that there is a problem with the premises somewhere but it's just so hard to find. Here's what I mean:
(NOTE: A lot of what I'm writing here is paraphrased lecture notes. So some credit should go to William Grey for teaching this stuff to me)
Parmenides makes the following claim:
1) Anything inquired into either exists or doesn't exist.
2) We can know nothing of what does not exist because it is impossible to think about what does not exist.
3) Only things that exist can be thought of.
4) Anything that can be thought about and can exist must exist, for it can exist and nothing (i.e. what does not
exist) cannot exist.
5) Therefore, in reference to premise one only the first alternative is possible: if something can
be thought about it actually exists.
The first thing that must be cleared up is that Parmenides is a monist - he believed that the world is made up on only one type of matter. Modern philosophy tends to like to split things up a bit more and determine between a physical and a mental world and such. Not so for Parmenides.
The temptation when faced with the above argument is to attack premise 3 and say "I'm thinking about a unicorn crossed with an echidna and THAT doesn't exist.". This argument only really works when one defines real as meaning something like 'exists in the empirically observable world'. For Parmenides the things that you think about or imagine are just as 'real' as the things that you see and smell so the animal you described is certainly real. We tend to have enormous confidence in calling our everyday experiences 'real' and describing people who experience hallucinations as having an experience that is less real. In some ways we really are being terribly overconfident in making this claim, Nick Bostrom argues that it is, in fact, more likely than not that we are living in a simulated computer experiment. In any case it's not unimaginable that in the future all of our now private mental events may become empircally observable hense breaking down the real/unreal barrier.
ANYWAYS, MOVING ON...
Parmenides come to a few unsettling conclusions...
A) Suppose that something came into existence.
B) Then there was a time when it did not exist.
C) So we are committed to talking about what (at some time) does not exist.
D) But we cannot talk about what does not exist.
E) So it makes no sense to talk of something beginning to exist.
The same argument works to say that it makes no sense to say that things ever cease to exist.
All pretty interesting stuff I thought. I've got a few criticisms and ideas about Parmenides theories but I'll let them ferment in my mind a bit before I try and express them here. I think next week we'll be looking at Zeno's paradoxes so I might make a post about that too. Fun fun. :)