24.00 F19 Lecture Handout 11: Incompatibilism

1 Handout 11 Incompatibilism 1. Van Inwagen’s Argument Determinism (v.I, p.186): (a) For every instant of time there is a proposition that expresses the state of the world at that instant. (b) If A and B are any propositions that express the state of the world at some instants, then the conjunction of A with the laws of physics entails B. Law of physics – a law of nature that is not about the voluntary behavior of rational agents Free will – the power or ability of agents to act otherwise than they in fact do. Case: A judge J had the opportunity to raise his hand at time T to pardon somebody but he did not. L = the laws of physics P = a proposition that expresses the state of the world at T P0 = a proposition that expresses the state of the world at a time before the judges birth, T0 From p.191: 1. If determinism is true, then the conjunction of P0 and L entails P. 2. If J had raised his hand at T, then P would be false. 3. If (2) is true then if J could have raised his hand at T, J could have rendered P false. 4. If J could have rendered P false, and if the conjunction of P0 and L entails P, then J could have rendered the conjunction of P0 and L is false. 5. If J could have rendered the conjunction of P0 and L false, then J could have rendered L false. 6. J could not have rendered L false. 7. If determinism is true, J could not have raised his hand at T. 2. Defending the Premises 2.1. Defense of (4) Let “•” represent logical entailment. Suppose (P0 and L) • P It follows (by logic) that: (~P) • ~(P0 and L) So if you can make it the case that (~P) – that is, you can render P false – then arguably you can also make it the case that conjunction of P0 and L false. Van Inwagen, Peter. “The Incompatibility of Free Will and Determinism.” Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition 27, no. 3 (1975):185–99. © Springer. All rights reserved. 2 2.2 Defense of (5) If J could have rendered the conjunction of P0 and L false, then J could have rendered L false. Why? Because P0 expresses some state of the world before J’s birth, and so, van Inwagen thinks, J can’t render P0 false. This means that if he can render the conjunction false, that must be because he can render L false. 2.3. Defense of (6) Van Inwagen argues that if somebody could render a proposition false, then that proposition is not a law of physics. Which means that if J could have rendered L false, then L is not a law of physics. But by stipulation L is a law of physics. Why think that if somebody could render a proposition false then that proposition is not a law of physics? Suppose the following are both true: (A) Nothing ever travels faster than light (B) Jones a physicist can construct a particle accelerator that would cause protons to travel at twice the speed of light. (It follows from (A) that Jones will never exercise such a power). van Inwagen’s two claims: (A) and (B) are consistent, but (B) entails that (A) is not a law of physics. “surely it is a feature of any proposition that is a physical law that no one can conduct an experiment that would show it to be false.” (193) *Humeanism vs non-Humeanism about laws 3. Objections Objection 1: In day to day life we have criteria for determining whether an agent could have acted otherwise. These criteria determine what it means to say that an agent could have acted otherwise. These criteria make no mention of determinism so if you think free will and determinism are incompatible you’re confused. Response: Predestinarianism says (1) if an act is foreseen it’s not free (ii) all acts are foreseen by God. Clearly this view is incompatible with free will, but are ordinary criteria make no appeal to it. So the inference from “ordinary criteria for free will make no appeal to X” to “X is compatible with free will” is false. Objection 2: Quite the contrary - free will entails determinism! To say that someone acted freely requires that he acted. But to say that someone acted requires that the person caused the relevant phenomenon (e.g. hand rising to occur). If determinism is false then the hand-raising would be uncaused, in which case it’s not even an act to begin with. Van Inwagen, Peter. “The Incompatibility of Free Will and Determinism.” Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition 27, no. 3 (1975): 185–99. © Springer. All rights reserved. 3 Response: Causation is consistent with determinism. Objection 3: “Conditionalists” say that “S could have done X” means “If S had chosen to do X, S would have done X.” Response: What premise of the argument is the conditionalist going to deny? The crucial premise is premise (6). Suppose we substituted (6) J could not have rendered L false. with (6a) It is not the case that if J had chosen to render L false, J would have rendered L false. Van Inwagen says – (6a) still seems true, but let’s suppose for the sake of the argument that (6a) is false: that if J had chosen to render L false, J would have rendered L false. This would show that (6) does not mean the same thing as (6a) since (6), van Inwagen argued, is true. So either the conditionalist’s analysis is true, but so is (6a) (since (6) is) and the argument goes through, or the conditionalist’s analysis is false.