Libertarian Free Will: Is a sufficient cause sufficient?

This is not meant as an "Is the Pope Catholic" type question.

The debate over free will, encompassing the disagreements between compatibilist (free will and causal determinism are compatible) and incompatibilist positions, offers many challenges to understanding. Many of those challenges result from the difficulty of expressing our beliefs and intuitions about free will (or the lack thereof) in terms free of ambiguity.

Where ambiguity occurs in an argument, we can easily fall into a fallacy of ambiguity.

Premise 1 If Ali licks Frazier then Ali will be world champion.
Premise 2 Ali licks Frazier.
Conclusion: Ali will be world champion.

If the first premise is understood as "defeats in a pugilistic contest" and the second premise is understood as making contact with one's tongue then the argument would pass as absurd. An argument like that above is formally valid (if both premisses are true then the conclusion must be true) using one sense of the word but invalid where the senses of the word differ. We do not expect that Ali could win a world championship by tonguing Frazier.

Over the past week, I noticed a key opportunity for a fallacy of ambiguity in the free will debate.

Robert Kane's libertarian free will concept of Ultimate Responsibility calls for a free agent to supply a sufficient reason for one decision over another.

LFW critic Galen Strawson suggests that a free agent must have UR for any sufficient reason resulting in a decision, and argues that an infinite regress invariably results from the attempt.

"Sufficient reason" may drift in meaning within philosophy, and I wonder if this might be such a case.

The "Principle of Sufficient Reason" is credited to G. W. Leibniz:

But in order to proceed from mathematics to natural philosophy, another principle is required, as I have observed in Theodicy; I mean the principle of sufficient reason, namely, that nothing happens without a reason why it should be so rather than otherwise.

Philosophers have noted that Leibniz was a bit ambiguous about his PSR, and the principle remains a minority view while persisting as a controversial issue. Notably, the LFW advocate Peter van Inwagen charged that the PSR results in fatalism.

In addition to the PSR, philosophy includes the related concept of a "sufficient cause." The Stanford Encyclopedia of Philosophy duly notes the relationship between this type of sufficiency and the concept of causal determinism.

Modal logic has a similar concept, and Norman Swartz communicates it with his typical clarity:

Definition: A condition A is said to be sufficient for a condition B, if (and only if) the truth (/existence /occurrence) [as the case may be] of A guarantees (or brings about) the truth (/existence /occurrence) of B.

This definition also seems to accord with causal determinism, for we may suppose a deterministic model in which a subject A chooses option B based on causal factors (a,b,c,d,e,f) and can take no other course of action under the circumstances. The causes acting on subject A constitute a sufficient cause for B.

The ambiguity surrounding "sufficient" jumped out as an important issue as I was reading Strawson's LFW critique "Luck Swallows Everything." Given that Strawson conspicuouly grants the possibility of indeterminacy, how can he possibly mean to insist on a sufficient reason for every step of reasoning in a LFW model? I've yet to encounter a satisfying explanation for that question.

It seems clear that since any LFW model entails incompatibilism that therefore the model cannot assume causal determinism. As such, the question "Why did A choose B?" cannot be asked consistently as though the lack of an answer disrupts the model. Any would-be reductio ad absurdum must go beyond that question in order to smash the model.

Consequently, it also seems clear that any LFW model will need room for a type of causation beyond the sufficient cause. Where identical A's might cause B or ~B (B or not-B) A cannot be a sufficient cause for either outcome without a resulting contradiction. With tongue in cheek, I propose using the term "Barely Sufficient cause" to denote cases where the same cause serves to bring about differing outcomes under the same set of conditions.

The BS cause allows discussion of freely willed indeterministic causation minus the problem of begging the question.

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Commenter "Jack" at the "Philosophy, et cetera" blog also notes the causation problem:
"No matter which direction I decide to turn, S1 is a (sufficient) cause of my so deciding."


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Additional reading of Kane's views on LFW have assured me that he does not think solely in terms of sufficient causes when he develops his notion of Ultimate Responsibility. Isolated passages might offer the impression that Kane's UR is compatibilist in nature, because he asserts that sufficient reason might exist for a given free will decision and outcome. That scenario is deterministic on its face, but Kane stipulates that any such sufficient reason must in turn have its explanation in an indeterministic "Self-Forming Action" under the control of the agent. The latter highlights Strawson's problem with ambiguity that I pointed out in an earlier critique. Quoting Strawson, "When you act, you do what you do, in the situation in which you find yourself, because of the way you are."

Strawson's premise lends itself to an understanding at odds with Kane's description of UR, and as a result I judge it a failure in addressing Kane's view of LFW.