Abstract detail

Title Aristotle on Homoeomerous Substances

There are two key places in Aristotle’s writings where the notion of Homoeomerous substances is discussed, one in Generation and Corruption and the other in Meteorology. They do not sit well together. In Generation and Corruption Aristotle uses the notion to characterise substances that result from a genuine composition of components rather than being merely mixed. The former are homoeomerous in the sense that any part of a substance resulting from a combination of A and B, however small, is itself a combination of A and B. Aristotle takes this to be in conflict with the notion of combination involved in the atomism of Democritus. In Meteorology Aristotle deals with homoeomerous substances in a more rough and ready way. Water and metals are cited as examples of homoeomerous substances while trees and eyes are given as examples of non-homoeomerous substances. This makes common sense. However, it is clear Aristotle attributes an inner structure to his ‘homoeomerous’ substances. Water is presumed to possess pores so that substances dissolve in it if the size and shape of their parts match that of the pores in the water. This implies that neither water nor the substances dissolved in it are homoeomeous as defined in Generation and Corruption. To resolve the tension I suggest it is necessary to distinguish between the project of describing the ultimate constitution of matter, the issue discussed in Generation and Corruption, and more down to earth projects designed to explain the properties of macroscopic materials by appeal to some microstructure.

Primary author
Alan Chalmers