In my MCCC Logic class tonight I'm thinking of presenting neurophilosopher David Chalmers's philosophically famous zombie argument against physicalism.
It will serve as an illustration of modus tollens, and hopefully will be fun and generate some discussion if I can get at least some of the students to understand it.
On "zombies" see here.
For Chalmers's argumment see here.
- If physicalism is true, then there cannot possibly be a world that contains zombies. (That is, there cannot be a world that is a physical duplicate of ours [that is, where everything is physically like in our world], which is not a duplicate simpliciter of our world [that is, which does not contain anything more or less than what our world contains].)
- But zombies are conceivable. (A "zombie" is a creature that is physically exactly like us, except that it lacks conscious experience.)
- Therefore, physicalism is false.
The argument's logical form is modus tollens:
- If p, then q.
- Therefore, not-p.
Here's another way to express this argument:
1. If zombies are logically possible, then zombies are metaphysically possible.
2. If zombies are metaphysically possible, then physicalism is false.
3. Zombies are conceivable.
4. If zombies are conceivable, then zombies are logically possible.
5. Zombies are logically possible. (from 3 and 4, MP)
6. Zombies are metaphysically possible. (from 1 and 5, MP)
7. Physicalism is false. (from 2 and 6, MP)