 There are two other possibilities. First, one may hold that when p entails q and there is some evidence e for p, it is p itself that is evidence for q. For example, it may be held that given that I have adequate evidence for believing that 2 is a prime number, I can use that very proposition (that 2 is a prime number) as an adequate reason for believing that there is at least one even prime. (See Klein 1981, 1995, and 2000, but see below for reasons for doubting that this is a genuine possibility.) Second, there are cases where the order is reversed because q serves as part of the evidence for p. For example, suppose that I am justified, ceteris paribus, in believing that (pure) water is present if I am justified in believing that there is present, at standard temperature and pressure, a clear, odorless, watery-tasting and watery-looking fluid that contains hydrogen and oxygen. This pattern is typical of abductive inferences, and is often referred to as “inference to the best explanation”. (See Vogel 1990, 2014b for a discussion of Cartesian Skepticism and inference to the best explanation.) In addition, there are cases in which it seems that some contraries of h need to be eliminated prior to h’s being justified. For example, reconsidering the zebra-in-the-zoo case, it seems to be true that if I had some good reason to think that the animals are cleverly disguised mules, such a contrary would need to be eliminated before I would be justified in believing that the animals were  zebras.[8]