Nathan on global justification
N. M. L. NATHAN suggests that regressive concepts of justification are particularly unhelpful when applied to suspicions or doubts about the truth-value of one's entire system of beliefs ('Evidential Insatiability', ANALYSIS 47.2, March 1987, pp. 110-15). Suppose one wants to be assured that one's belief-system contains only true beliefs. To be so assured requires some evidence, and having such evidence in the form of proposition q requires one to actually believe q. Nathan rejects the possibility that such an evidential proposition q could already be a member of one's beliefsystem, because 'you cannot assure yourself that a conjunction is true by citing as evidence for its truth a proposition which is a member of the same conjunction' (p. 114). And if q isn't already believed, then adding it to one's beliefs produces a new set of beliefs about which similar suspicions can be formulated. Evidence for the new set will be evidence for q itself (since q counts as the evidence for the original set); the new evidential proposition can't, on Nathan's grounds, already be believed; and the problem begins anew, and so on, ad infinitum. While Nathan subscribes to scepticism about justifying entire belief-systems regressively, he is more sanguine about the possibilities of justification for single propositions. He argues that the search for evidence q for belief p might take one through a regression of beliefs q1, q2, q3,... which could terminate with belief qn which itself does not require any further justification. 'It would do', he states, 'for you to believe that, quite independently of whether you have evidence for it, q, is a proposition which you cannot help believing' (p. 112; emphasis added). Consider, then, a proposition of the following sort: