But if we couldn't resort to metaphorical fictions, it's doubtful whether we could even form conceptual representations of such nebulous phenomena as "ideas", thoughts", "minds", and so forth. The bearing of these ideas on current thinking on speech origins remains unclear. One suggestion is that ape communication tends to resist the metaphor for social reasons. Since they inhabit a Darwinian (as opposed to morally regulated) social world, these animals are under strong competitive pressure "not" to accept patent fictions as valid communicative currency. Ape vocal communication tends to be inflexible, marginalizing the ultra-flexible tongue, precisely because listeners treat with suspicion any signal which might prove to be a fake. Such insistence on perceptible veracity is clearly incompatible with metaphoric usage. An implication is that neither articulate speech nor distinctively human abstract thought could have begun evolving until our ancestors had become more cooperative and trusting of one another's communicative intentions. When people converse with one another, according to the American philosopher John Searle, they're making moves, not in the real world which other species inhabit, but in a shared virtual realm peculiar to ourselves. Unlike the deployment of muscular effort to move a physical object, the deployment of illocutionary force requires no physical effort (except the movement of the tongue/mouth to produce speech) and produces no effect which any measuring device could detect. Instead, our action takes place on a quite different level — that of "social" reality. This kind of reality is in one sense hallucinatory, being a product of collective intentionality. It consists, not of "brute facts" — facts which exist anyway, irrespective of anyone's belief — but of "institutional facts", which "exist" only if you believe in them. Government, marriage, citizenship and money are examples of "institutional facts". One can distinguish between "brute" facts and "institutional" ones by applying a simple test. Suppose no one believed in the fact — would it still be true? If the answer is "yes", it's "brute". If the answer is "no", it's "institutional". The facts of language in general and of speech, in particular, are, from this perspective, "institutional" rather than "brute". The semantic meaning of a word, for example, is whatever its users imagine it to be. To "do things with words" is to operate in a virtual world which seems real because we share it in common.