In attempting to formulate the relation between this new world of ideas and immediate sense-experience, Plato constructed his scheme of substantiation and participation. The Platonic doctrine of substantiation and participation is an expression of the conviction that anything so valuable as Socrates had shown ideas to be could not be merely formal or unreal. Up to the discovery of these ideas reality lay in the "substances" of perception. Hence in order to have that reality to which their worth, their value in life, entitled them, the ideas must be substantiated.
This introduction of the newly discovered ideas into the world of substances and reality wrought, of course, a change in the conception of the latter--a change which has well-nigh dominated the entire philosophic development ever since. Let us recall that the aim of Socrates was to find something that would prevent society from going to pieces under the influence of the disintegrating conception of experience as a mere flux of given immediate content. Now, in the concepts Socrates discovered the basis for just this much-needed wholeness and stability. Moreover, the fact that unity and stability were the actual social needs of the hour led not only to the concepts which furnished them being conceived as substantial and real, but to their being regarded as a higher type of reality, as "more real" than the given, immediate experiences of perception. They were higher and more real because, just then, they answered the pressing social need.
The ideas supplied this unity because they furnished ends, purposes, to the given material of perception. The given is now given for something; for something more, too, than mere contemplation. Socrates also showed, by the most acute analysis, that the content of these ends, these purposes, was social through and through.
From the ethical standpoint this teleological character of the idea is clearly recognized. But as "real," the ideas must be stated in the metaphysical terms of substance and attribute. Here the social need is abstracted from and lost to sight. The fundamental attributes of the ideas are now a metaphysical unity and stability. Hence unity and stability, wholeness and completeness, are the very essence of reality, while multiplicity and change constitute the nature of appearance. Thus does Plato's reality become, as Windelband says, "an immaterial eleaticism which seeks true being in the ideas without troubling itself about the world of generation and occurrence which it leaves to perception and opinion."[164]