Peter van Inwagen: "An Argument for Incompatibilism"

Van Inwagen's first version of the consequence argument for the incompatibility of free will and determinism

[@opoleboy]

Excellent explanation of argument thank you. I have a class on it today, and was a little put off by its logical/propositional presentation in the text. Once again thanks great to listen to you. You have a nice voice, pace, and clear structure of thoughts.

[@MrGoplo]

Great video and awesome explanation

[@danwylie-sears1134]

This seems like a completely unreasonable criterion of free will. In this universe, you didn't; therefore, you couldn't have? No: in a counterfactual universe indistinguishable from ours up to the present -- in particular, in a universe in which you still count as you -- you did. There's nothing more than that, that free will could possibly be expected to require, and still count as free will. Any more stringent requirement is either simple nonsense or an ersatz "free will" concocted to prop up a prior commitment to incompatibilism.

[@HGWells1]

That doesn't affect the argument in any way. If the possible world you're describing were, as you stated, indistinguishable from ours up to the present, then the laws of physics and the past movement of all particles would be identical. In that case, the present moment would be identical, as every moment is the direct result of the moment that immediately preceded it. So there is still no possible world indistinguishable from ours up to the present moment, in which you acted differently at the present moment. Any possible world must, as you say, be indistinguishable from ours up to the present, including the laws of physics and the movement of the particles. In that case, there isn't a difference between invoking possible worlds, or just using our own, as a possible world in which you don't perform identical actions in the present is actually impossible, and therefore not a possible world.

[@danwylie-sears1134]

@@HGWells1 Indistinguishable doesn't mean atom-by-atom identical.

[@HGWells1]

@@danwylie-sears1134If it didn't mean this, then how would it be indistinguishable from the past to the present?

[@danwylie-sears1134]

@@HGWells1 ​ @HGWells1 If every cubic millimeter of the universe has the same temperature and pressure as they do in the real world, but all the locations of atoms are randomly reassigned within each cubic millimeter of gas or liquid that's not part of a human brain, that's indistinguishable. Everyone has the same memories, and the world is exactly the same in any way that would provide any evidence about the past. But the butterfly-effect stuff gets re-randomized both into the past and into the future. Into the past, it doesn't make any difference because otherwise it wouldn't have wound up indistinguishable. Into the future, the probability that it will make a difference is one, because there's no choose-the-counterfactual mechanism to stop it.