2015.11.16 The Consequence Argument
The topic What is free will? Some paradigm cases. (linked to concepts like coercion, action, and esp. praise and blame) The claim that we don t have free will.... Free will, metaphysics, and ethics.
Incompatibilism Determinism Let P 0 be a complete description of the world at the beginning of time, and in general let P t be the complete description of the world at time t. Let L be a complete description of the real laws of nature. Then, for every t, P 0 and L jointly entail P t. (two pictures: determinism and the Garden of Forking Paths) Laplace s demon; epistemology vs. metaphysics Incompatibilism If determinism is true, then there is no free will. Compatibilism is the claim that incompatibilism is false.
van Inwagen s Argument: basic concepts Some truth is up to us if some action of ours could have changed whether it is true or not. Some truth is untouchable if it couldn t have been up to anyone. The intuitive idea: untouchable truths are out of our control and can t be affected by us.
van Inwagen s Argument 1 The Necessity Rule: If a truth is a necessary truth, then a truth is an untouchable truth. 2 The Conditional Rule: If it is an untouchable truth that p, and it is an untouchable truth that if p then q, then it is an untouchable truth that q. 3 It is necessarily true that: if P 0 and L are true, then Peter van Inwagen writes the essay The Consequence Argument. (by the definition of determinism) 4 It is necessarily true that: if P 0 is true, then: if L is true, then Peter van Inwagen writes the essay The Consequence Argument. (equivalent to (3) by logic) 5 It is an untouchable truth that: if P 0 is true, then: if L is true, then Peter van Inwagen writes the essay The Consequence Argument. (by (1) and (4))
van Inwagen s Argument cont. 6 It is an untouchable truth that P 0 is true. (since P 0 is in the distant past, and so not up to any of us) 7 It is an untouchable truth that: if L is true, then Peter van Inwagen writes the essay The Consequence Argument. (2, 5, and 6) 8 It is an untouchable truth that L is true. (since the laws of nature are not the kinds of things that anyone can change) 9 It is an untouchable truth that Peter van Inwagen writes the essay The Consequence Argument. (2, 7, and 8)
Principle of Alternate Possibilities Principle of Alternate Possibilities (PAP) If a person is responsible for something, then they could have done otherwise. 1 PAP 2 If it is an untouchable truth that Peter van Inwagen wrote the essay The Consequence Argument, then he could not have done otherwise. (by the intuitive characterization of untouchable ) 3 Peter van Inwagen is not responsible for writing the essay The Consequence Argument.
David Lewis objection The argument equivocates on untouchable. Distinguish Untouchable 1 Some truth is untouchable if no one could have caused it to be different. Untouchable 2 Some truth is untouchable if it wouldn t have been different, no matter what anyone did. Read the argument with untouchable understood as untouchable 2. Then either P 0 or L are not untouchable. Read the argument with untouchable understood as untouchable 1. Then the conditional rule is false. For you can cause something to be different even if it follows logically from past events. Either the past events or the laws would then be different (and so not untouchable 2 ) but you needn t cause them to be different.
What if determinism isn t true? The argument assumes determinism, but determinism is arguably false. Two lines of reply: 1) The argument can be supplemented to show that we have no free will if determinism is false, also. If an action is not determined, then it is random; if an action is random, then it is not free. 2) The assumption of determinism can be weakened. The argument used determinism only to say that your actions are entailed by some description of the world before your birth this may be compatible with indeterminism at a very small scale.
Taxonomy Determinism The world is deterministic. Indeterminism The world is not deterministic. Hard Determinism The world is deterministic; if the world is deterministic, then we do not have free will; and, we do not have free will. (Determinism + Incompatibilism) Soft Determinism The world is deterministic, and we do have free will. (Determinism + Compatibilism + we do have free will) Libertarianism The world is not deterministic; if the world is deterministic, then we do not have free will; and, we do have free will. (Indeterminism + Incompatibilism + we do have free will)