One of the problems with believing in the principle of sufficient reason, which stipulates that there are no contingent facts which have not a sufficient explanation, is when it comes to the doctrine of Libertarian free will. The Libertarian is committed to saying that a person’s decision is in principle free of any necessary constraint, such that any free decision is neither the product of the situational circumstance in the context of which it is taken, nor is it a function of ‘quantum’ randomness. Thus, when Susie freely chooses ‘x’ instead of ‘y’, her choice was in principle unpredictable – even if one were aware of the conjunctive set of all causal factors influencing Susie at the moment of her choice, one would not be able to determine with certainty what she would choose, since her choice is not the result of causal necessity. This libertarian view, articulated by William James, among others, is obviously an implicit rejection of physicalism or materialism. The libertarian may not need to say that, if one were aware of the whole situational circumstance, they could not stipulate some reasonable probability conjecture about what Susie might freely decide to do – but applying probability in these cases is misleading since no two situational circumstances are ever really the same, regardless of how similar. For the single entire situational circumstance in which Susie has the choice between x and y, there are only two logically possible worlds – one in which Susie chooses x, and another in which she chooses y.
However, the Libertarian is also committing herself to a rejection of the strong principle of sufficient reason, or so argues William Lane Craig. In an interesting article on Craig’s website Craig defends his Molinism against what is called the ‘grounding objection’. He says:
Davison thinks that “Molinists must simply accept the truth of counterfactuals of creaturely freedom logically prior to creation as a brute, unexplained fact.”10 Here I think we see the real root of the problem. Grounding Objectors have difficulty accepting the existence of brute facts. These latter-day Leibnizians want everything to be brought into submission to the Principle of Sufficient Reason, including facts concerning human free choices. They want an explanation even for why counterfacts about free creaturely choices obtain. Such a demand bears out what I have suspected all along: Grounding Objectors are implicitly presupposing a non-libertarian view of freedom, for counterfactuals of creaturely freedom are no more inexplicable than certain categorical, present-tense statements about the actual situation of free agents, e.g., “Jones is freely writing a letter to his wife.” We can have all the truth-making we want for such a statement but what we cannot have on a libertarian view is an explanation of why Jones freely so acts.
~ Ducking Friendly Fire: Davidson on the Grounding Objection
Now, Alexander Pruss, in his book simply and appropriately titled the principle of sufficient reason addresses the libertarian concern, sketching three ways in which a robust libertarian may be able to satisfy the principle of sufficient reason. He suggests first that the choice itself may explain itself sufficiently, just as necessary truths explain themselves sufficiently (eg. what is the sufficient reason why two and two make four). Another explanation, to which I am very attracted, is that the sufficient reason that Susie chose x instead of y just is all the reasons that Susie had for choosing x. This is both a sufficient explanation of why Susie chose ‘x’, and it is not an explanation of the kind which would negate the libertarian commitment to actual freedom. Some objectors would say that while it may seem to be a sufficient explanation of why Susie chose ‘x’, it is not a sufficient reason for why Susie chose ‘x’ rather than ‘y’, to which Pruss has an excellent response on his blog here.
I think we may be able to argue, alternatively (in the case that the Molinist doesn’t accept this argument for libertarian free will decisions not being brute facts) that if we accept a weaker version of the same Leibnizian principle WPSR we might be committed to saying that for any contingent proposition, where an explanation along the lines of sufficiency is even possible, there is some sufficient explanation. By the nature of the case it may not be possible to posit a sufficient reason why Susie chose x ‘rather than’ y, it seems as though there can plausibly be sufficient reason for the truth of Counterfactuals. The Molinist has to convince us that no such explanation is even possible (which she may plausibly do by citing the libertarian nature of the counterfactuals in question. Remember though that there can be sufficient reason for why Susie freely choose x, even if there is not sufficient reason why she chooses x instead of y. Thus, a counterfactual of the Molinist type, the Molinist must argue, is always of the form “Susie, if placed in E situational circumstance, would freely choose ‘x’ RATHER THAN ‘y’.” (and thus that nothing makes this true).
In any case, coming back to the idea that the sufficient reason Susie chooses ‘x’ just is the set of all reasons Susie had for closing ‘x’, I would like to say that it seems to me to be profoundly consonant with Augustinian thinking; For Augustine one could not choose any option to which they were not attracted, since without having some reason for choosing ‘x’, the option does not present itself as ‘live’ and thus cannot be ‘chosen’. That is why Thomas Aquinas says that man is ‘free’ to the extent that he is rational.
I think that William Lane Craig may be mistaken (excusably) about wanting to say that believing in ungrounded Molinist-type counterfactuals is really no worse than wanting to believe in libertarian free will decisions.