For, indeed, if it were maintained that any One is the result of a mixture of several constituents suppose, that is, that things were many and moved into one another, and that their mixture were either by way of the composition of the many in one, or, being due to the constituents fitting in with one another, resulted in their covering one another from view then in the former case the constituents mixed would be easily discernible, if you separated them; whilst, if they covered one another, rubbing would reveal each constituent, the successive layers being uncovered as the upper layers were removed.