On the other hand, says Bloom, we have moral responses — such as prohibitions on homosexuality — which don't make evolutionary sense, yet seem to be part of a catch-all protective disgust-response to what is harmful to the survival and well-being of the original small-scale society. And other moral attitudes, such as outrage at slavery, have emerged over the course of human history: our feeling that slavery is terribly wrong was not shared by people hundreds of years ago.

Custom is king of all, said Herodotus. "We are most influenced by the behaviours that we see repeatedly," says Bloom. Other, alarming studies show children being more inclined to give to a charity box if they saw adults doing it first, and even more readily inclined to copy ungenerous behaviour. But Bloom in effect proves the moral relativists wrong in thinking this is pure copycat behaviour. We are born trailing clouds of glory, with a surprisingly rich array of moral equipment. 

But this innate morality needs to be nurtured, strengthened and encouraged throughout our childhoods. How? 

Bloom calls religious belief the "accelerant to morality — part of a self-reinforcing system" that is reinforced further by society's system of justice. Participation in the religious community, which strengthens societal bonds, is the most powerful aspect of religion. But Bloom does not presume to spell out much of an answer to the question that forms grimly in the parental mind: when religious belief breaks down, what remains to reinforce the system? 

"He feels bad because he was proud of his tower and you knocked it down." "If you throw snow on their [side]walk, they will have to clean it up all over again." According to another psychologist, Martin Hoffmann, children receive about 4,000 such "inductions" every year — statements which urge them to see things from another's perspective and build empathy. 

What lucky children are these! I have a terrible feeling that not all of us, let alone parents such as that mother I overheard on the bus, are making up our full 4,000. How far removed are the lives of so many children, who encounter violence, anger, selfishness, cruelty and indifference every day, from the sweet and reasonable world of Yale babies?