Full Idea
Awakened reason distinguishes color from size and shape from body and then shape and size from the substance of body, and so by drawing distinctions and abstracting, it arrives at a grasp of the substance of body, which supports size, shape and color.
Gist of Idea
By comparing qualities and features, reason can gradually infer the nature of substance
Source
Robert Grosseteste (Commentary on 'Posterior Analytics' [1226], I.14), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 07.4
Book Reference
Pasnau,Robert: 'Metaphysical Themes 1274-1671' [OUP 2011], p.130
A Reaction
This optimistic view influenced Aquinas, and is called 'incrementalism' by Pasnau. It is the spirit of scientific essentialism, and a nice instance of inference to the best explanation (though 'substance' in itself explains virtually nothing).