The things that puzzle us as adults begin by puzzling us as children, or this has certainly been the case for me. In the late 1940s society in which I grew up, there were three things you were never supposed to ask questions about. One of them was money, especially how much of it anyone made. The second was religion: to begin a conversation on that subject would lead directly to the Spanish Inquisition, or worse. The third was sex. I grew up among the biologists, and sex – at least as practised by insects – was something I could look up in the textbooks that were lying around the house: the ovipositor was no stranger to me. So the burning curiosity children experience vis-à-vis the forbidden was focused, for me, on the two other taboo areas: the financial and the devotional.

We kids of the 1940s did usually have some pocket money and, although we weren’t supposed to talk about it or have an undue love of it, we were expected to learn to manage it at an early age. When I was eight years old, I had my first paying job. I was already acquainted with money in a more limited way – I got five cents a week as an allowance, which bought a lot more tooth decay then than it does now. The pennies not spent on candy I kept in a tin box that had once held Lipton tea. I understood that these pennies could be traded for goods such as ice-cream cones but I did not think them superior to the other units of currency used by my fellow children: cigarette-package airplane cards, milk-bottle tops, comic books and glass marbles of many kinds. Within each of these categories, the principle was the same: rarity and beauty increased value. The rate of exchange was set by the children themselves, though a good deal of haggling took place.