So, what is free will, really? Well, there’s enough answers to that question that another one can’t hurt. I consider free will to be the ability to consider the choices that one may make and decide among them. That would make the sensation of free will the feeling that one is considering choices and deciding between them.

This really boils down to what “ability” is though, and for all that it seems superficially simpler, it seems to be fundamentally tougher concept. I had corn flakes for breakfast today, but I could have had Cheerios — or could I have? This happened this morning, the past is fixed, so I couldn’t have had Cheerios because I didn’t. What does it mean to say “I could have had Cheerios.” when “I had Cheerios.” is false?

It means I was considering what to eat, and Cheerios was a choice under consideration. When we make choices, we model (consider) the result of the choices, and it’s to that model that “I could have …” refers.

The human mind is extremely complicated and poorly-understood. Let’s consider a far simpler system: A chess program on a computer. Does it have free will? Well, it needs to make decisions: Does it move this pawn, sac that knight, develop that rook? It calculates the results of all these possible actions, as thoroughly as it is able, and decides upon a move.

It goes through a lot of effort, but the programmer who designed it could tell you exactly why it chooses the move: It calculated this series of moves as being the best for both sides as near as it could figure, resulting in this board position, which it evaluated as superior to the board positions from the other possible moves, blah blah blah, the point is as a consequence of its programming it couldn’t have done anything other than queen takes pawn.

Those of us outside the program see it that way, but the program has to consider all these other moves. It has to model their consequences. It does a ton of calculation, and eventually makes a decision. It “could” have sacrificed the knight, in the sense that the decision mechanism has to consider that possibility. It “couldn’t” have done so, in the sense that its decision mechanism has to reject it.

I “could” have played hooky from work yesterday, in the sense that my decision mechanism considered the possibility and modeled the consequences. I “couldn’t” have played hooky, in the sense that my decision mechanism rejected it. That feeling of your decision mechanisms in action is the sense of free will.