As long as Plato’s philosophy continued to shape their thought, men went on speaking more or less traditionally of Ideas as real supersensible beings. When, however, the Aristotelian mode of thinking superseded the Platonic, the term ‘Idea’ ceased to be used in its original sense; so much so that, when Locke and other modern philosophers resorted to it in order to describe the content of the mind, they did so in complete obliviousness of its first significance.