In the last posting, I pointed out that the free will problem is usually framed as the question of whether freedom is possible in a deterministic universe. One reply to this question (as we’ll see, it’s not the only one) is to say that if the universe is deterministic, then free will doesn’t exist. This view is known as incompatibilism.

Most philosophically uneducated people (including many psychologists) are incompatibilists. To most people, it seems like no-brainer that if your choices are caused by prior events, then those choices just can’t be free.  

Of course, philosophers who endorse incompatibilism give reasons why they hold this position. The standard sort of argument runs along the following lines:

  1. To have free will, a person has got to have real options – that is, for any choice that a person freely makes, it’s got to have been possible for them to have chosen differently.
  2. If the universe is deterministic, then everything that happens is caused by prior events. Because of this, there are no real options. It’s impossible for anyone to have chosen differently than they in fact did.
  3. Therefore, if the universe is deterministic then nobody has free will.

Let me this out with a concrete example. Suppose that you are offered a choice between two flavors of ice cream – chocolate and vanilla – and you choose chocolate. Incompatibilists claim that this was a free choice only if in exactly the same circumstances you could have chosen vanilla instead – only if your decision was genuinely up for grabs. They further claim that if determinism is true, then you simply couldn’t have opted for vanilla; so, if the universe is deterministic, your decision to have chocolate ice cream wasn’t really a free one.

It’s important to spell out a couple of aspects of incompatibilism that are easy to miss, but are important for understanding it.

The first of these is that incompatibilists don’t have to accept that the universe is deterministic. All that they are committed to is the view that IF the universe is deterministic, THEN freedom doesn’t exist.  As a matter of fact, some incompatibilists believe that the universe is fully deterministic while others reject this claim. We’ll examine the details of these two positions a little further down the road.

The second thing to notice is that incompatibilists don’t draw the conclusion that if the universe is not deterministic, then freedom does exist, for the simple reason that this would a logical fallacy. Let me explain why….

Logic is concerned with the relationship between premises and the conclusions that they are supposed to underwrite.  Philosophers use the term valid for arguments in which the truth of the premises guarantees the truth of the conclusion (notice that this isn’t the same as the meaning of ‘valid’ in vernacular speech). It’s the structure of an argument that makes it valid (or invalid). Consider this silly little argument:

  1. If Pete is a porcupine, then Pete is a mammal.
  2. Pete is a porcupine.
  3. Therefore, Pete is a mammal.

You can see straight away that this is a valid argument: if its premises are true then its conclusion has got to be true. Now contrast it with a blatantly invalid argument.

  1. Pete is a porcupine, then Pete is a mammal.
  2. The sky is blue.
  3. Therefore, Pete is a mammal.

In this case, the premises don’t get us to the conclusion. The argument is invalid, and invalid arguments are fallacious.

Now, getting back to our main topic, suppose that Imogen the incompatibilist reasoned like this:

  1.  If the universe is deterministic, then freedom doesn’t exist.
  2. The universe isn’t deterministic.
  3. Therefore, freedom exists.

Imogen would be committing a fallacy, because the conclusion of her argument doesn’t follow from its premises. If you’ve never studied logic this may not be obvious to you, so I’ll make it clear by using a different example with the same structure.  Imagine someone using the following pattern of reasoning to convince you that they have a pet beagle:

  1. If my pet is a cat, then it isn’t a beagle.
  2. My pet isn’t a cat.
  3. Therefore, my pet is a beagle.

Would you be convinced by this argument?  Of course not!  That would be crazy, wouldn’t it?  Obviously, it doesn’t make sense for a person to say that if her pet isn’t a cat then it must be a beagle.  But some people try to recruit quantum physics on behalf of free will in the following way, without realizing that it’s just as crazy:

  1. If the universe is deterministic, then free will doesn’t exist.
  2. Quantum physics proves that the universe isn’t deterministic.  Subatomic particles behave indeterministically.
  3. Therefore, quantum physics proves that free will exists.

It’s every bit as wacky to say that if the universe is indeterministic then free will exists as it is to say that if my pet isn’t a cat then it must be a beagle.

That’s all for now.  Stay tuned for the next installment.

You are reading

Philosophy Dispatches

Freedom in a Deterministic World

Free Will 101, Part 6: Compatibilism

Is Free Will a Myth?

Free Will 101, Part 5: The Conceivability Problem

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