In this post I will examine one way of unpacking the concept of what it means for a belief to be causally sustained by some bit of evidence (whether propositionally or non-propositionally understood)—namely, Marshall Swain’s notion of a counterfactual cause. We may define a counterfactual in terms of possible world semantics. Following Lewis let us say that the truth of the statement A > B consists in the fact that, among possible worlds where A holds, there is at least one world where B holds and which is more similar to our world than any world where A holds but B does not. (For the sake of simplicity, I will just speak in terms of the closest possible world.)
Roughly, the idea is that a belief, B, is based on a reason, R, if R is either the non-deviant cause or counterfactual cause of B. R counterfactually causes B if in the closest possible world where the actual cause, C, is missing, R causes B. Thus, causal theorists maintain that the underlying intuition behind the causal theory can be preserved by insisting that if the justifying evidence does not actually cause belief, it must counterfactually cause belief. Applied to the ‘Fanatical Tom’ counterexample, we may say that in closest possible world in which Tom’s belief that SPY is not caused by his fanatical religious views, it is caused by the spyware evidence. Thus, the spyware evidence is the counterfactual cause of Tom’s belief.
We may add one important restriction to the idea of a counterfactual cause. First, it is crucially important that we limit ourselves the closest possible world. Otherwise, the notion of a counterfactual cause would become much too broad; allowing beliefs to be based on reasons when it is obvious that they are not so based in the actual world. (Presumably, it is such considerations that prompt Swain to limit the application of the concept of a counterfactual cause to the reason next in line to the reason that actually causes the belief.) Thus, Swain’s view may be put as follows:
S1: Subject S bases her belief that p on R IFF S’s having R is either (i) a cause of S’s believing that p in the actual world, or (ii) S’s having R is a counterfactual cause, such that R causes S’s believing that p in the closest possible world in which the actual cause, C, is absent.If we accept the restriction on what constitutes a counterfactual cause imposed by S1, we seem able to adjust the ‘Fanatical Tom’ counterexample so that the spyware is no longer the counterfactual cause of Tom’s belief. For example, we could imagine that Tom is not only a religious fanatic, but that he is also a member and ardent believer in a webring devoted to conspiracy theories. Thus, holding all other parts of the ‘Fanatical Tom’ counterexample constant, we may stipulate that in addition to his fanatical religious views, he has also read about the NSA’s surveillance activities on the internet, before actually discovering the spyware evidence in Fred’s home. On this revised version of ‘Fanatical Tom’ case the closest possible world in which Tom’s belief is not based on his religious views, it would actually be based on his reading the conspiracy theory webring. Thus, according to S1, the spyware no longer constitutes a counterfactual cause for Tom’s believing that SPY. Since in the re-described case, Tom’s belief seems no less justified than it is the original case, the introduction of counterfactual causes fails to resolve the present difficulty.
But perhaps Swain is being unnecessarily conservative when he restricts the notion of a counterfactual cause to the closest possible world. Perhaps it would be sufficient to restrict ourselves to nearby worlds in which Tom both finds the spyware and believes SPY. On the present proposal, we might be able to rescue Swain’s theory by widening the scope of what counts as counterfactual cause to all worlds sufficiently close to the actual world. Thus modified, Swain’s counterfactual cause may be summarised thus:
S2: Subject S bases her belief that p on R IFF S’s having R is either (i) a cause of S’s believing that p in the actual world, or (ii) for some set, C, of possible counterfactual causes of S’s belief that p, R is a member of C.On S2, R need not be the next in line to the actual cause, C, such that in the closest possible world in which C is not the actual cause R causes S’s belief that p. It is sufficient that R be the cause of S’s belief that p in some nearby world. As with most talk of nearby worlds, there is an obvious difficulty regarding how one delineates which worlds count as nearby and which do not. Or, to put the problem differently, how do we determine (in a non-arbitrary manner) which reasons, out of the maximal set of possible reasons, ought to qualify as counterfactual reasons.
One plausible criterion would be to restrict ourselves to reasons that are occurrent to the subject in the actual world. Thus, we may add to S2 the clause that for some possible reason, R, to be included in the set, C, of possible counterfactual causes, it must be occurrent to S in the actual world. Assuming that this provides a plausible and sufficient restriction on which worlds ought to count as nearby, we seem to have a working definition of a counterfactual cause. S2 provides us with a reply to the ‘Fanatical Tom’ example since it allows both the conspiracy webring and the spyware (along with any other potential reasons occurrent to Tom in the actual world) to be considered a counterfactual cause of his belief.
Unfortunately, this still is not sufficient for rescuing the notion of a counterfactual cause. An even more decisive objection to the Swainesque reply to the ‘Fanatical Tom’ problem is that it allows the spyware to be the counterfactual cause of Tom’s belief even when it seems obvious that it is not justified. For example, suppose that Tom’s religion teaches him to reject all evidential relations and that only beliefs based upon ‘faith’ are justified. However, Tom realises that his neighbour, Fred, still buys into ‘the whole evidence thing’ and appeals to the spyware solely for the purpose of converting Fred. The idea is that Tom does not see the spyware as genuine evidence himself. In such a case, Tom’s belief would clearly be unjustified. However, in such a scenario, the spyware would still be the counterfactual cause of Tom’s belief by Swain’s lights. In the closest possible world in which Tom no longer has his religious beliefs, and in which he still believed SPY, his belief would be based on the spyware. This is because in that world, the religious belief would no longer prevent Tom from recognising the spyware as a reason for believing SPY. Thus, Swain’s notion of a counterfactual cause allows the spyware to causally sustain a belief even when it is clear that the belief is not justified.
I believe the above analysis suggests that all attempts to cash out the idea of a belief being causally sustained by evidence in terms of counterfactual causation is moribund. In my next post on this topic I will present what I believe is a successful reply to Lehrer Gypsy-Lawyer type scenarios.