But it was Descartes who, by working it out with scientific exactness, perfectly developed and completed it. And this is just what brought its fallacy to light, as demonstrated by Spinoza, Locke, and Kant successively. It was demonstrated by Spinoza; because his philosophy consists chiefly in the refutation of his master's twofold dualism, and because he entirely and expressly denied the two Substances of Descartes, and took as his main principle the following proposition: “Substantia cogitans et substantia externa una eademque est substantia, quae jam sub hoc, jam sub illo attribute comprehenditur.” It was demonstrated by Locke; for he combated the theory of innate ideas, derived all knowledge from the sensuous, and taught that it is not impossible that Matter should think. And lastly, it was demonstrated by