Are some parts of reality more fundamental than others? Physics is often said to be more fundamental than biology, because the physical facts are thought to explain the biological facts. But is the world really divided into levels in this way? Naomi Thompson argues that, in fact, we project this structure onto reality, rather than discovering it there. This structure tells us about our ways of understanding and explaining the world, but it does not tell us about reality as it is in itself.

Are universities, chairs and tables, money, and viruses real? On the one hand it seems that they are – we can study at university, thump our fists onto tables, exchange money for food and develop treatments (or fail to do so, with devastating consequences). But on the other hand, these things all seem to depend on other things: universities are plausibly nothing more than the buildings they are located at, the staff that work at them and the students that populate them; chairs and tables are made up of molecules of various kinds; for something to be money seems to depend somehow on our collective decision-making; and viruses are just groups of proteins working together. If these things can be fully explained and accounted for in terms of the things they depend on (as plausibly they can) then perhaps only what they depend on is really real. And if, for example, the chairs and tables are ultimately just made up of subatomic particles, perhaps those are the only things that are really real?