What is free will, really? Steven Pinker explains.

I do believe that there is such a thing as free will, but by that, I do not mean that there is some process that defies the laws of physical cause and effect. As my colleague Joshua Greene once put it, it is not the case that every time you make a decision a miracle occurs. So I don't believe that.

I believe that decisions are made by neurophysiological processes in the brain that respect all the laws of physics. On the other hand, it is true that when I decide what to say next, when I pick an item from a menu for dinner, it's not the same as when the doctor hits my kneecap with a hammer and my knee jerks. It's just a different physiological process, and one of them we use the word free will to characterize the more deliberative, slower, more complex process by which behavior is selected in the brain.

That process involves the aggregation of many diverse kinds of information – our memory, our goals, our current environment, our expectation of how other people will judge that action. Those are all information streams that affect that process. It's not completely predictable in that there may be random or chaotic or nonlinear effects that mean that even if you put the same person in the same circumstance multiple times, they won't make the same choice every time.

Identical twins who have almost identical upbringings, put them in the same chair, face them with the same choices. They may choose differently. Again, that's not a miracle. That doesn't mean that there is some ghost in the machine that is somehow pushing the neural impulses around. But it just means that the brain, like other complex systems, is subject to some degree of unpredictability.

At the same time, free will wouldn't be worth having and certainly wouldn't be worth extolling in world discussions if it didn't respond to expectations of reward, punishment, praise, blame. When we say that someone – we're punishing or rewarding someone based on what they chose to do, we do that in the hope that that person and other people who hear about what happens will factor in how their choices will be treated by others and therefore there'll be more likely to do good things and less likely to do bad things in the expectation that if they choose beneficial actions, better things will happen to them.

So paradoxically, one of the reasons that we want free will to exist is that it be determined by the consequences of those choices. And on average, it does. People do obey the laws more often than not. They do things that curry favor more often than they bring proprium on their heads but not with 100 percent predictability. So that process is what we call free will. It's different from many of the more reflexive and predictable behaviors that we can admit, but it does not involve a miracle.