 Holism may be defended by a slippery-slope argument. It seems that we can imagine Sanjay’s and Ani’s beliefs about the nature of fish and the members of the class of fish slowly diverging. At some point, it will seem plainly correct to say that even though they may both say “salmon are fish”, they are not expressing the same belief by that sentence. As an extreme case, we might imagine Ani to be so benighted as to hold that to be a “fish” is neither more nor less than to be an Earthly animal in regular contact with Martians, and that only salmon, whales, leopards, and banana slugs are in such contact. But if we deny, in the extreme case, that Ani and Sanjay share the same belief, expressed by the sentence “salmon are fish”, it seems artificial to draw a sharp line anywhere in the progression of divergence, on one side of which they share exactly the same belief about salmon and on the other side of which they have divergent beliefs. One is thus led to the conclusion that similarity in belief is a matter of degree, and it may then be difficult to avoid accepting that even a relatively small divergence in surrounding beliefs may be sufficient to generate subtle differences between two beliefs expressed in the same words. Similar slippery slope arguments can be constructed that emphasize gradual belief change in concept acquisition (“Leibniz was a metaphysician” agreed to before and after learning philosophy) or gradual change in surrounding theory or in the meaning of a term (“electrons have orbits” as uttered by Niels Bohr in 1913 and as uttered by Richard Feynman in 1980). (This argument is similar in some ways to Stalnaker’s argument for a possible-worlds analysis of the propositional contents of belief—see §3.1, above—and indeed Stalnaker takes himself, there, to be committed to holism.)