People do not think in English or Chinese or Apache; they think in a language of thought. This language of thought probably looks a bit like all these languagesBut compared with any given language, mentalese must be richer in some ways and simpler in others.

For one thing, before the 20th century, there were plenty of genocides. We tend to forget about them, partly because they weren't as well documented and partly because, until recently, people didn't care. We used euphemisms like 'sackings' and 'sieges' instead of calling them 'genocides.'

The moral, then, is that familiar categories of behavior - marriage customs, food taboos, folk superstitions, and so on - certainly do vary across cultures and have to be learned, but the deeper mechanisms of mental computation that generate them may be universal and innate.

Equality is not the empirical claim that all groups of humans are interchangeable; it is the moral principle that individuals should not be judged or constrained by the average properties of their group.

An enormous amount of scientific language is metaphorical. We talk about a genetic code, where code originally meant a cipher; we talk about the solar system model of the atom as though the atom were like a sun and moon and planets.

My opinions about human nature are shared by many psychologists, linguists, and biologists, not to mention philosophers and scholars going back centuries.

I think that metaphor really is a key to explaining thought and language. The human mind comes equipped with an ability to penetrate the cladding of sensory appearance and discern the abstract construction underneath - not always on demand, and not infallibly, but often enough and insightfully enough to shape the human condition. Our powers of analogy allow us to apply ancient neural structures to newfound subject matter, to discover hidden laws and systems in nature, and not least, to amplify the expressive power of language itself.