And now, if we move forward a dozen centuries and compare Thomas Reid and Immanuel Kant from this same point of view, we find the same conception of man again triumphant. But there is an essential difference: Kant carried all before him because he based himself on an age-old view of human nature, whereas Reid, uncomprehended up to our own day, pointed to a picture of man only just then dawning on the horizon of the future. Just as through Pelagius there sounded something like a last call to European humanity not to forget the cosmic nature of the soul, so through Reid the memory of this nature announced its first faint renewal. It is common to both that their voices lacked the clarity to make themselves heard among the other voices of their times; and with both the reason was the same: neither could perceive in fullness - the one no longer, the other not yet - the picture of man which ensouled their ideas. The certainty of Reid's philosophical instinct, if such an expression be allowed, and at the same time his tragic limitations, due to an inability fully to understand the origin of this instinct, come out clearly in the battle he waged against the 'idea' as his immediate predecessors understood it. We know that Plato introduced this word into the philosophical language of mankind. In Greek ιδέα (from ιδεῑν, to see) means something of which one knows that it exists, because one sees it. It was therefore possible to use the word 'to see' as Plato did, because in his day it covered both sensible and supersensible perception. For Plato, knowing consisted in the soul's raising itself to perceiving the objective, world-forming IDEAS, and this action comprised at the same time a recollection of what the soul had seen while it lived, as an Idea among Ideas, before its appearance on earth. 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 When, however, the Aristotelian mode of thinking superseded the Platonic, the term 'Idea' ceased to be used in its original sense; so much so that, when Locke and other modern philosophers resorted to it in order to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. It is thus that in modern philosophy, and finally in ordinary modern usage, 'idea' came to be a word with many meanings. Sometimes it signifies a sense-impression, sometimes a mental representation, sometimes the thought, concept or essential nature of a thing. The only thing common to these various meanings is an underlying implication that an idea is a purely subjective item in human consciousness, without any assured correspondence to anything outside.