(It will have to be the belief that p, for some proposition p). Plantinga thought that we have something of an idea as to the history of NP properties: structures with these properties have come to exist by small increments, each increment such that it has proved to be useful in the struggle for survival. But he then asked how the content property of a belief came about: "How does it [the content] get to be associated in that way with a given proposition?" He said that materialists offer two theories for this question: According to the first, content supervenes upon NP properties; according to the second, content is reducible to NP properties. (He noted that if content properties are reducible to NP properties, then they also supervene upon them.) He explained the two theories as follows: Reducibility: A belief is a disjunction of conjunctions of NP properties. Strong Supervenience (S+): For any possible worlds W and W* and any structures S and S*, if S has the same NP properties in W as S* has in W*, then S has the same content in W as S* has in W*. Supervenience can either be broadly logical supervenience or nomic supervenience. Plantinga argued that neural structures that constitute beliefs have content, in the following way: "At a certain level of complexity, these neural structures start to display content. Perhaps this starts gradually and early on (possibly C. elegans [a small worm with a nervous system composed of only a few neurons] displays just the merest glimmer of consciousness and the merest glimmer of content), or perhaps later and more abruptly; that doesn't matter. What does matter is that at a certain level of complexity of neural structures, content appears. This is true whether content properties are reducible to NP properties or supervene on them." So given materialism some neural structures at a given level of complexity acquire content and become beliefs. The question then is according to Plantinga: "what is the likelihood, given materialism, that the content that thus arises is in fact true?" This way of proceeding replaced the first step of Plantinga's earlier versions of the argument. Criticism by eliminative materialists The EAAN claims that according to naturalism, evolution must operate on beliefs, desires, and other contentful mental states for a biological organism to have a reliable cognitive faculty such as the brain. Eliminative materialism maintains that propositional