a1 King's College, London
Aristotle says in the De Sensu that other colours are produced through the mixture of black bodies with white (440a31–b23). The obvious mixture for him to be referring to is the mixture of the four elements, earth, air, fire, and water, which he describes at such length in the De Generatione et Corruptione. All compound bodies are produced ultimately through the mixture of these elements. The way in which the elements mix is described in i. 10 and 2. 7. They mix in such a way as to produce an entirely new substance, in which the characteristics of the original earth, air, fire, and water survive only in modified form.