Suppose you're in the Science Center and in the cafe looking for something to eat. You hesitate between having a low-fat yogurt and one or two slices of pizza. The pizza looks good ("puffy, hot") but you know it's chubby-making. You decide to have pizza and forget yogurt but after plowing through your pizza - you eat it with a gusto - you have a twinge of regret. The next day you look in the mirror, get on the scale you have in your room from Target and you say to yourself "I wish I hadn't eaten that pizza. I could have had yogurt instead."
"I could have had the yogurt instead."
What does this mean, and is it even true?
Well, yogurt was available when you were going through the cafeteria line: you had the opportunity ("Don't we live, in fact, in a land of opportunity"?) to buy the yogurt. But this (surely) is not all that you mean. You mean you could have taken yogurt instead of those enormous (blankity-blank) slices of pizza. You did not just have an opportunity. You could have done something other than what you actually did. Before you made up your mind and resolved to have pizza, it was still open to you to buy the yogurt.
This still doesn't seem to be quite enough. When you say to yourself "I could have had yogurt instead," you don't mean only that if you had chosen yogurt, you would have had yogurt, you also mean you could have chosen yogurt - no "ifs" about it. That's why you're so angry with yourself now; and why you blame yourself for having taken and eaten those darn (blankity-blank) "enormous" slices of pizza.
What you are saying to yourself is not, for instance, if only Frieda had been there: she eats like a sparrow and she would never eat pizza at any time of the day, and if she had been there, you would have chosen yogurt. What you are saying is that you could have chosen yogurt instead of pizza, just then, as things actually were.
This is an idea of "can" or "could" which we attribute to most people (and perhaps some animals). When you say "My car can climb to the top of Mt. Washington," you mean, I presume, that your car has enough power to reach the top of Mt. Washington without conking out on the way up. You don't mean that, on occasion, your car just takes off for the top of mountains rather than sitting in the driveway. Something else has to happen first. You have to get into your car and start the engine, etc., etc.. But when it comes to people, we seem to believe that they can do various things that they actually don't do or haven't done, just like that, without anything else happening differently first. What does this mean?
Part of what it means may be something like the following: Nothing up to the point at which you choose (remember the yogurt and the pizza) determines irrevocably what your choice will be. It remains a real, live possibility that you will choose yogurt right up to the moment when you choose the pizza. Your choice of pizza wasn't determined in advance. There were no processes or forces at work before you made up your mind to have pizza that made it inevitable that you would choose pizza.
If it was really determined in advance that you would choose pizza, it could not be true that you could have chosen yogurt instead. Why you are so upset with yourself, so angry, why you now blame yourself for having taken pizza instead of yogurt is because you (you yourself) closed off the possibility of having yogurt when you chose the slices of pizza.
You did it!
Now some people (they shall remain nameless) believe that it is never possible for us to do anything other than what we in fact do. The sum total of a person's experiences, desires and knowledge, his or her genetic make-up, the social circumstances and the nature of the choice facing the person, together with other factors that we may not be able - right off the bat - to identify, all add up to make a given action in a given set of circumstances inevitable.
Given your constitution and history and psychological profile at that very moment, you had to choose pizza. There are laws of nature (we may not know all of them just yet) which govern everything that happens in the world, which govern our actions and choices as well as the planets and the temperature at which water comes to a boil, that combine with a set of circumstances and conditions that determine whether a given action will occur or a particular action will be taken, no "ifs," "ands" or "ors" about it, and these circumstances and conditions in keeping with the laws of nature rule out any other possibility.
Now if this were true, then even while you were making up your mind whether to choose low-fat yogurt or pizza, it was being determined by the factors at work that you would choose pizza. You could not have chosen yogurt at that moment in that place. And since you could not, you should stop blaming yourself for having acted as you did.
Now some scientists believe that for certain very tiny particles such as photons it is not determined in advance where one or another of these very tiny particles will be. What if, human actions, at least some of them, are not determined in advance? Just as it is (as it were) an open possibility where a given photon might be at any given moment, it is an open possibility what you will or will not choose.
But is this enough to make sense of and to leave room for free will? Is this all you mean when you say "I could have chosen yogurt instead?" No, you believe something more. You believe you determined what you would do, by doing it. It wasn't determined in advance, but it didn't just happen either.
You determined it.
But if it wasn't determined in advance by your desires, and beliefs and personality, among other things, it seems to be something that just happened without any explanation. And this is odd, very odd. Things don't just happen. How can you determine what you do, if nothing determines it?
One way out of this apparent puzzle is to argue that antecedent causal determination does not threaten freedom of choice - only a certain kind of cause does that. Indeed one might claim that for an action to be your doing, it has to be produced by certain kinds of causes in you. So when you chose pizza instead of yogurt, what you did, did not just happen; you wanted pizza more than you wanted yogurt. Your appetite for pizza was greater than your appetite for yogurt and stronger than your desire - at that moment - to avoid foods that are chubby-making. In other cases the psychological explanation for your choice will be more complex, but there will always be one - otherwise that action wouldn't be yours. For an action to be your doing doesn't require that there be no antecedent determining cause at all: it just means that the cause has to be of the right, familiar psychological sort.
But this does not seem to get us anywhere. If you think that your choice of the pizza was determined by your circumstances and your psychological condition, you would feel trapped. And if you thought the same of everyone else, albeit they would be acting under different circumstances and different psychological conditions, you would view them as puppets. People aren't puppets. And if they were, it wouldn't make sense to hold them responsible for their actions any more than it makes sense to hold your car responsible for refusing to start in the morning.
On the other hand, it makes little sense to hold a person responsible for anything that he or she does unless we believe the person determined his or her action. What does it mean to say that you determine your actions, if nothing about you determines the action? Perhaps to say that you could have had yogurt instead is a philosophical illusion. The Question then becomes: "What would you and the world have to be like for it to be true that you could have had yogurt instead of pizza?"
- - adapted from Thomas Nagel's What Does It All Mean?