 In addition, the theory of evolution by natural selection apparently provides a non-semantic, non-intentional basis upon which to explicate functions and, in turn, semantic content. Individual organisms vary in their characteristics, such as how their neurons respond to features of the environment. Some of these differences in how neurons respond make a difference to an organism’s survival and reproduction. Finally, some of these very differences may be heritable. Natural selection, commonly understood as this differential reproduction of heritable variation, is purely causal. Suppose that there is a population of rabbits. Further suppose that either by a genetic mutation or by the recombination of existing genes, some of these rabbits develop neurons that are wired into their visual systems in such a way that they fire (more or less reliably) in the presence of dogs. Further, the firing of these neurons is wired into a freezing behavior in these rabbits. Because of this configuration, the rabbits with the “dog neurons” are less likely to be detected by dogs, hence more likely to survive and reproduce. Finally, because the genes for these neurons are heritable, the offspring of these dog-sensitive rabbits will themselves be dog-sensitive. Over time, the number of the dog-sensitive rabbits will increase, thereby displacing the dog-insensitive rabbits. So, natural selection will, in such a scenario, give rise to mental representations of dogs. Insofar as such a story is plausible, there is hope that natural selection and the genesis of functions can provide a naturalistically acceptable means of delimiting content-determining causes.