Anaximenes explained all substantial differences through quantitative degrees of condensation.

Evidence

The fundamental substance, he said, is air. The soul is air; fire is rarefied air; when condensed, air becomes first water, then, if further condensed, earth, and finally stone. This theory has the merit of making all the differences between different substances quantitative, depending entirely upon the degree of condensation. — Bertrand Russell, History of Western Philosophy, 172

Categorization

• corroborated: 2 independent passages support this claim — Bertrand Russell, History of Western Philosophy, 172