Chemistry is “concerned”, as Benfey (1963, 574) puts it in his opening sentence, “with substances and with their transformations into other substances”. But the central notion of substance has a chequered history which hasn’t clearly led to a single simple unified concept. The general notion can be approached from a microscopic or a macroscopic perspective. The macroscopic perspective reflects, perhaps, the culmination of an older historical tradition, but has by no means been surpassed by the microscopic perspective which has developed since the beginning of the twentieth century.