This post was originally made on July 15, 2013.
This is a philosophical post instigated by Scott Aaronson’s recent paper and blog post regarding free will. A lot hinges, I think, on how one phrases the question. I like the question “When do choices exist?” as opposed to “Do people have free will?”. I will take two passes at this question. The first is a discussion of game theory. The second is a discussion of coloquial language regarding choice. My conclusion is that choices exist even when the decision making process is deterministic.
Game Theory. Game theory postulates the existence of choices. A bimatrix game is defined by two matrices each of which is indexed by two choices — a choice for player A and a choice for player B. Given a choice for each player the first matrix specifies a payout for player A and the second matrix specifies a payout for player B. Here choices exist by definition.
We write programs that play games. A computer chess program has choices — playing chess involves selecting moves. Furthermore, it seems completely appropriate to describe the computation taking place in a min-max search as “considering” the choices and “selecting” a choice with desirable outcomes. Note that most chess programs use only deterministic computation. Here the choices exist by virtue of the rules of chess.
It seems perfectly consistent to me to assume that my own consideration of choices, like the considerations of a chess program, are based on deterministic computation. Even if I am determined and predictable, the world presents me with choices and I must still choose. Furthermore, I would argue that, even if I am determined, the choices still exist — for a given chess position there is actually a set of legal moves. The choices are real.
Coloquial Language. Consider a sentence of the form “she had a choice”. Under what conditions do we colloquially take such a sentence to be true? For example, we might say she had a choice between attending Princeton or attending Harvard. The typical condition under which this is true is when she was accepted to both. The fact that she was accepted to both says nothing about determinism vs. nondeterminism. It does, however, imply colloquially that the choice exists.
The issues of the semantics of natural language are difficult. I plan various blog posts on semantics. The central semantic phenomenon, in my opinion, is paraphrase and entailment — what are the different ways of saying the same or similar things and what conclusions can we draw from given statements. I believe that a careful investigation of paraphrase and entailment for statements of the form “she had a choice” would show that the existence of choices is taken to be a property of the world, and perhaps the abilities of the agent to perform certain actions, but not a property of the fundamental nature of the computation that makes the selection.
Summary. It seems to me that “free will” cannot be subjectively distinguished from having choices. And we do have choices — like the chess program we must still choose, even if we are determined and predictable.