The Argument of Parmenides

Just for fun, see if you can recreate the way we wrote the argument out in class. (Much of the work comes from M. Cohen's work on the history of Ancient philosophy):

1) A thing can be thought about only if it is possible for it to exist.

2) Anything that does not exist, cannot exist.

But 2 is equivalent by contraposition to:

3) Anything that can exist, does exist.

From (1) and (3) it follows that:

4) A thing can be thought about only if it exists.

which is also equivalent by contraposition to:

5) Anything that does not exist, cannot be thought about.