"Minds are in limited supply, and each mind has a limited capacity for memes, and hence there is considerable competition among memes for entry in as many minds as possible. This competition is the major selective force in the memosphere, and, just as in the biosphere, the challenge has been met with great ingenuity. For instance, whatever virtues (from our perspective) the following memes have, they have in common the property of having phenotypic expressions that tend to make their own replication more likely by disabling or preempting the environmental forces that would tend to extinguish them: the meme for faith, which discourages the exercise of the sort of critical judgment that might decide that the idea of faith was, all things considered a dangerous idea; the meme for tolerance or free speech; the meme of including in a chain letter a warning about the terrible fates of those who have broken the chain in the past; the conspiracy theory meme, which has a built-in response to the objection that there is no good evidence of a conspiracy: "Of course not – that's how powerful the conspiracy is!" Some of these memes are "good" perhaps and others "bad"; what they have in common is a phenotypic effect that systematically tends to disable the selective forces arrayed against them. Other things being equal, population memetics predicts that conspiracy theory memes will persist quite independently of their truth, and the meme for faith is apt to secure its own survival, and that of the religious memes that ride piggyback on it, in even the most rationalistic environments. Indeed, the meme for faith exhibits frequency-dependent fitness: it flourishes best when it is outnumbered by rationalistic memes; in an environment with few skeptics, the meme for faith tends to fade from disuse."