In my last post, I discussed libertarianism. Just to remind you, libertarianism is the view that determinism is false and that our choices are radically free. Just as theists believe that God is the first cause—the uncaused cause of everything that exists—libertarians believe that human agents are the first cause of their own choices. We're all, so to speak, miniature dieties.
When libertarians claim that determinism is false, they don’t mean to say that nothing can be explained deterministically. That would be ridiculous. When you turn the key in the ignition of your car, this normally makes the car start. If the car doesn’t start when you perform this action, then you can rest assured that there’s something that causally accounts for it. No sane person would maintain that if your car fails to start that’s because it chooses not to, because cars don’t have any options. They are not architects of their own futures. To use a bit of philosophical jargon, there aren’t any alternative possibilities open to a car.
Libertarianism rests on two pillars. The first pillar is the denial of the claim that human beings are exhaustively deterministic systems. In contrast to the situation for cars, there are alternative futures available to us. The second pillar is the assertion that we forge these futures through autonomous acts of choice. These acts are radically free in virtue of standing outside the vast web of causation bind the macroscopic cosmos together. This sort of high-octane freedom, which philosophers call contra-causal freedom, is needed (it is claimed) to account for the ostensible fact that we are morally responsible for our actions. It’s only because humans choose freely that are beings who are deserving of praise or blame.
For libertarianism to be plausible, both of these claims have got to stand up to careful scrutiny. Let’s see how they do.
The first pillar sits on pretty solid ground, given that most particle physicists deny that the subatomic world is indeterministic. Things just happen without anything making them happen. Now if the physicists are right about this, all that it shows is that determinism is false (and therefore that hard determinism is false) but it doesn’t establish that we are contra-causally free
If this seems odd to you, try thinking about it this way. The claim, “If determinism is true, then we are not free” has the same form as “If someone’s only car is a Toyota, then that person doesn’t have a Ford.” Suppose someone were to say “The fact that Katie’s only car isn’t a Toyota proves that her car is a Ford.” That would be a ludicrous argument, because it’s just plain obvious that not having a Toyota doesn’t require Ford-ownership!
This principle holds true of all statements that have the same sort of structure. True statements of the form “If P then Q” simply don’t license the move from this to “not-P, therefore not-Q.”
Now, let’s apply this to the issue at hand. Suppose that if determinism is true than we aren’t free, and suppose determinism isn’t true. This doesn’t lead to the conclusion that we are free that we’re not not-free) because the falsity of determinism doesn’t entail the truth of contra-causal freedom (think again of the car example). That’s why libertarians need the second pillar. But this is precisely where they meet a massive and, I think, insurpountable problem. It’s known as the intelligibility problem. Let me walk you through it step-by-step.
The first is a logical point. Any statement of the form “P or not-P” is always true. For example, “Santa is coming to town or Santa is not coming to town,” “An animal is a porcupine or it’s not a porcupine,” “God exists or God doesn’t exist.” In all othe these cases, either the fist statement (“P”) or the second statement (“not-P”) must be true because there isn’t any third option.
So, we can be sure that the following statement is true:
(1) Our choices are determined by prior events or they aren’t determined by prior events.
The second step is to try on the first of these options.
(2) Suppose that our choices are determined by prior events.
Next, for the sake of the argument, let’s grant the libertarian premise, and see where it takes us:
(3) If our choices are determined by prior events, then we aren’t free.
Well, then, what about the second option?
(4) Suppose that our choices aren’t determined by prior events.
The next premise is the most interesting piece of the argument. If you carefully think this through, you will realize that if our choices aren’t determined by prior events then they aren’t up to us, and can’t really be considered free choices. Imagine that every decision in your life had to be made by flipping a coin (coin flips aren’t really indeterministic, but they are a good analogy for indeterministic processes). Would this make you free? Suppose a mysterious benefactor were to knock on your door and offer you a choice between a desiccated grasshopper and a check for a million dollars. Would choosing by a flip of a coin make your choice a free choice? I think not. Now, imagine that your brain flips a neural coin every time you make a choice. As the coin example shows us, this would make you unfree. So…
(5) If our choices aren’t determined by prior events, then we aren’t free.
Now, given that there are only two options (either our choices are determined or they’re not determined) and both entail that we’re not free, we’re driven to the conclusion that:
(6) We’re not free.
Both hard determinism and libertarianism are premised on the truth of incompatibilism (the position expressed above in the third premise). But what if incompatibilism is false—in other words, what if it’s not true that freedom is impossible in a deterministic universe? Many (in fact, most) philosophers nowadays deny that incompatibilism is true. They embrace a position known as compatibilism. This will be the topic of the next and final article in this series on free will.