 We see, then, that for Foucault the key to Classical knowing is the idea, that is, mental representation. Classical thinkers might disagree about the actual ontological status of ideas (their formal reality); but they all agreed that as representations (epistemically, if not ontologically) they were “non-physical” and “non-historical”; that is, precisely as representing their objects, they could not be conceived as having any role in the causal networks of the natural or the human worlds. From this it further followed that language—precisely as a physical and/or historical reality—could have no fundamental role in knowledge. Language could be nothing more than a higher-order instrument of thought: a physical representation of ideas, having no meaning except in relation to them.