 This thought, according to Foucault, led to some important and distinctively modern possibilities. The first was developed by Kant himself, who thought that representations (thoughts or ideas) were themselves the product of (“constituted” by) the human mind. Not, however, produced by the mind as a natural or psychological reality, but as belonging to a special epistemic realm, transcendental subjectivity. Foucault contends that Kant maintained the Classical view that knowledge cannot be understood as a physical or historical reality, but he located the grounds of knowledge in a domain (the transcendental) more fundamental than the ideas it subtended: subjectivity insofar as it is the condition of the possibility of thinking and judging. However, Kant did not think of transcendental subjectivity as located on a level of being beyond reality; it was not an unfounded postulate of metaphysical speculation. According to Foucault, such metaphysical notions were developed later by post-Kantian idealists such as Hegel. Another—and in some ways more typically modern—view was that ideas were themselves historical realities. This could be most plausibly developed, as Herder did, by tying ideas essentially to language, now regarded as the primary (and historicized) vehicle of knowledge. But such an approach was not viable in its pure form, since to make knowledge entirely historical would deprive it of any normative character and so destroy its character as knowledge. In other words, even when modern thought made knowledge essentially historical, it had to retain some functional equivalent of Kant’s transcendental realm to guarantee the normative validity of knowledge.