 One way to solve the problem for the analysis of fallibilistic knowledge is to focus, not on the entailment relation, but rather on the probabilistic relation holding between the subject’s justification and the proposition believed (see Reed 2002 and 2013). When the subject knows that p on the basis of justification j, and P(p/j) is less than 1, the subject’s knowledge is fallibilistic. (Although epistemologists will disagree about what the appropriate conception of probability is, here is a crude example of how probability may figure in a fallibilistic epistemology. A basic historical reliabilist will say that a belief is justified just in case it has been produced by a process that has yielded a preponderance of true beliefs. So, if the process has yielded a true belief, say, 90% of the time, the probability that the next belief will be true is 90%; this is so even if the belief in question is necessarily true and has been logically deduced from a set of beliefs, each of which is necessarily true.) Adapting this solution to the problem for certainty, we can say that the subject is certain that p when P(p/j) = 1, where j is the justification or grounds for the belief (see Van Cleve 1977 and Lewis 1952). However, in order for j to impart a probability of 1 to p, it must also be the case that P(j) = 1. That is to say, j must be certain for the subject before it can make anything else certain. But, if we are to explain the certainty that p by appeal to the certainty that j, we fall into a vicious regress. The only way to stop it is to allow that some beliefs may have an intrinsic probability of 1 (see Russell 1948, p. 396, and Van Cleve 1977). It is, however, difficult to see how intrinsic probability of this sort is possible (barring, of course, a subjectivist account of probability, which could, in any case, capture only psychological certainty).