Are chemical entities real?

Talking of atoms, molecules, bonds and reactions is so essential to chemistry’s practice that questioning their existence might seem a strange thing to do. However, it is an open question in philosophy whether this chemical ‘stuff’ actually exists; a question that is surprisingly difficult to answer!

The main reason for this difficulty lies in that chemical entities are – strictly speaking – unobservable. In general, the more one moves towards very small (and very large) energy, length and time scales, the more difficult it is to experimentally access the entities that purportedly exist at those scales. Observing such entities and measuring their properties requires making conjectures and inferences about the world. So, to establish the reality of chemical entities one needs to look at how chemistry is (and has been) done. Among other things, this involves evaluating how scientists justify their theories and what sort of approximations and idealisations they make, as well as the criteria with which they establish the predictive and explanatory success of their theories.