The message from history is so blatantly obvious - that free trade causes mutual prosperity while protectionism causes poverty - that it seems incredible that anybody ever thinks otherwise. There is not a single example of a country opening its borders to trade and ending up poorer.

Our minds have been built by selfish genes, but they have been built to be social, trustworthy and cooperative.

You need to understand how human beings bring together their brains and enable their ideas to combine and recombine, to meet and, indeed, to mate. In other words, you need to understand how ideas have sex.

The fuel on which science runs is ignorance. Science is like a hungry furnace that must be fed logs from the forests of ignorance that surround us. In the process, the clearing we call knowledge expands, but the more it expands, the longer its perimeter and the more ignorance comes into view.

It is not a zero sum game. The simple idea of the gains from trade lies at the heart of the modern and the ancient economy, not the power of capital. There is nothing else to it.

The average Mexican lives longer now than the average Briton did in 1955. Infant mortality is lower today in Nepal than it was in Italy in 1951. The proportion of Vietnamese living on less than $2 a day has dropped from 90 per cent to 30 per cent in twenty years. The rich have got richer, but the poor have done even better.

We consciously decide whether to consider people; we fall in love despite ourselves; we entirely fail to fall in love with people who fall in love with us. It is a mightily complicated business.