Free will vs Causality – Something has to give!

Many people believe that everything must have a cause. I argue elsewhere that the notion of cause is highly problematic, and either ambiguous or meaningless in most of its uses within philosophy. But let’s leave that aside, assume we know what a cause is, and consider where it leads.

If everything has a cause then all our actions have a cause. Say I lift my arm to hail a taxi. We might imagine a chain of causes, working backwards from the physical action of my arm, to nerve impulses, to brain commands, to brain processing (deciding do I really want a taxi? Do I want that taxi?), to sensory stimuli (seeing the taxi).

Hailing a taxi can happen with our brain entirely on auto-pilot. What about a more deliberate and conscious decision, one with grave moral repercussions? Consider the anti-hero Meursault in Camus’s novel L’Etranger. He shoots a man dead for no very good reason. Is there a similar train of causes leading to this action as there was to hailing the taxi?

What, if anything, was the cause of Meursault’s brain reaching the decision to pull the trigger? We might suppose it was because he was mean or vicious, or perhaps he had a suppressed love of violence. Why did he have those characteristics? Was it his genes, or perhaps a product of his early environment? Perhaps it was a history of past cruel and callous acts he has done that has lowered his inhibitions to pulling the trigger. But then what caused those acts?

We can go back and back and back. If we can trace the causes back to events that occurred before Meursault was conceived, then free will cannot have played any role in his decision. What are the alternatives? I think the following list is exhaustive:

  1. The chain of causes ends with an event in Meursault’s brain (or ‘mind’, if we prefer) that was uncaused. It just happened without a cause. Perhaps that is what libertarians mean by free will.
  2. The chain of causes ends with an event outside Meursault’s brain/mind, while he was alive, that was uncaused.
  3. The chain of causes ends in a causal loop of events that occur while Meursault was alive.
  4. The chain of causes does not end. It undergoes an infinite regress. As we have assumed there are no causes prior to Meursault’s conception, this regress must occur within the finite time of Meursault’s life.

Of these options, 1 and 2 require denial that every event has a cause. 3 requires acceptance of causal loops and 4 requires acceptance of an infinite regress.

The usual notion of causality requires that a cause happens at a time earlier than its effect, which rules out causal loops (option 3) and requires that there is some time t0 to which the times of the causes in option 4 asymptotically approach (but never reach) as we trace backwards through the infinite causal regress. Further, t0 must be no earlier than the moment of Meursault’s conception. But then we can combine all the events in the causal chain occurring between t0 and t0+1 nanosecond and call that a single event. That event is not caused by any prior event, and hence is uncaused.

So this analysis presents us with a stark choice: either the action was caused by events before Meursault’s conception, and we must deny libertarian free will, or the action can be traced back to an uncaused event, in which case we must deny that every event has a cause.

What makes this interesting is that many Christian apologists try to assert both the existence of libertarian free will (as part of doctrines about original sin and salvation) and the necessity of every event being caused (as part of a classical cosmological argument for the existence of God). Based on the above analysis, it appears impossible to hold both beliefs. Either one must ditch universal causality (the ‘Principle of Sufficient Reason’ as it is sometimes called) or one must discard libertarian free will.

My current position is that I suspect neither belief is true. I can’t prove that, but I don’t need to – it is a perfectly plausible hypothesis. Equally, it seems plausible to believe one of the two but not the other. The problem arises when you wish to believe both.

There is nothing new in any of these arguments. They have all been made before, many times. But it strikes me as particularly stark and concise that belief in libertarian free will requires asserting a break in the chain of causality, whereas many of those that wish to hold that belief also assert in another context that everything must have a cause.