Morality is not just any old topic in psychology but close to our conception of the meaning of life. Moral goodness is what gives each of us the sense that we are worthy human beings.

As every student in Philosophy 101 learns, nothing can force me to believe that anyone except me is conscious. This power to deny that other people have feelings is not just an academic exercise but an all-too-common vice, as we see in the long history of human cruelty.

Since the point of erotica is to offer the consumer sexual experiences without having to compromise with the demands of the other sex, it is a window into each sex's unalloyed desires. Pornography for men is visual, anatomical, impulsive, floridly promiscuous and devoid of context and character. Erotica for women is far more likely to be verbal, psychological, reflective, serially monogamous and rich in context and character. Men fantasise about copulating with bodies; women fantasise about making love to people.

If we are not to abandon values such as peace and equality, or our commitments to science and truth, then we must pry these values away from claims about our psychological makeup that are vulnerable to being proven false.

When a scientist considers all high-tech mental machinery needed to arrange words into ordinary sentences, prescriptive rules are, at best, inconsequential little decorations. The very fact that they have to be drilled shows that they are alien to the natural workings of the language system. One can choose to obsess over prescriptive rules, but they have no more to do with language than the criteria for judging cats at a cat show have to do with mammalian biology.

Morality, then, is not a set of arbitrary regulations dictated by a vengeful deity and written down in a book; nor is it the custom of a particular culture or tribe. It is a consequence of the interchangeability of perspectives and the opportunity the world provides for positive-sum games.

Knowledge is a continuous fabric, in which ideas are connected to other ideas. Reason-free zones, in which people can assert arbitrary beliefs safe from ordinary standards of evaluation, can only corrupt this fabric, just as a contradiction can corrupt a system of logic, allowing falsehoods to proliferate through it.