Whenever and wherever it was discovered that the content of experience as given in immediate perception could be reconstructed through ideas, then and there began to emerge such questions as these: What is the significance of this reconstructive power? What is the relation between it and the immediate experience? What is the relative value of each in experience as a whole? What is their relation to truth and error? If thinking leads to truth, and thought must yet get its material from perception, how then shall the product of thought escape infection from the material? On the other hand, if truth is to be found in the immediate experience, can it here be preserved from the blighting effects of thought? For so insistent and pervasive is this activity of thought that it appears to penetrate into the sanctum of perception itself. Turning to a third possibility, if it should be found that truth and error are concerned with both--that they are products of the combined activity of perception and reflection--then just what does each do? And what in their operations marks the difference between truth and error? Or still again, if truth and error cannot be found in the operations of perception and reflection as such, then they must be located in the relation of these processes to something else. If so, what is this something else? Out of such questions as these is logic born. There may be those who will object to some of these questions as "logical" problems--those who would limit logic to a description of the forms and processes of reconstruction, relegating the question of the criterion of truth and error to "epistemology." This objection we must here dismiss summarily by saying that, by whatever name it is called, a treatment of the forms and processes of thought must deal with the criterion of truth and error, since these different "forms" are just those which thought assumes in attempting to reach truth under different conditions. Certainly in the beginning the Greeks regarded their newly discovered power of thought as anything but formal. Indeed, it soon became so "substantial" that it was regarded as simply a new world of fact, of existence alongside of, or rather above, the world of perception. But Socrates hailed ideas as deliverers from the contradictions and paradoxes into which experience interpreted in terms of immediate sense-perception had fallen. In the concept Socrates found a solution for the then pressing problems of social life. The Socratic universal is not a mere empty form which thought imposes upon the world. It is something which thought creates in order that a life of social interaction and reciprocity may go on. This need not mean that the Greeks were reflectively conscious of this, but that this was the way the concept was actually used and developed by Socrates.