The processes of logical thinking enter into practical life, and are still more indispensable in the building up of the sciences; for only by their means can ideas be rendered determinate. This use of Logic as an instrument of knowledge presupposes a certain correspondence between thought and reality, or, at any rate, between the laws which govern the one and the other. Hence we are led at once to the question which is fundamental for knowledge: how is the application of Logic possible?Two points which are intimately related call for special investigation:
1. As to whether and how the immutability of logical objects implies the persistence of a corresponding something in the world of Reality.
2. Whether there is anything in Reality corresponding to general and abstract concepts. With regard to the first question, we find four different attitudes have been taken up at various times by philosophical thought.
THE DOCTRINE OF THE ELEATICS
The principles of Logic imply the immutability of everything that is real; all that is is rational: hence change and motion have no real existence.
THE DOCTRINE OF HERACLITUS
Reality is a flux of sensuous things: hence nothing in it is rational. (Impossibility of the application of the logical principles.)
THE DOCTRINE OF HEGEL
Reason must overcome the contradiction between understanding, which constructs for itself unchangeable objects (by means of logical thinking), and empirical reality, in which everything is changeable. Hence we must create a higher Logic to supply the theory of the thought which transcends experience. Reality will be seen to be rational when it is looked at from the standpoint of this. so-called higher Logic (Dialectic).
DOCTRINE OF CRITICAL POSITIVISM
Critical Positivism regards the system of Hegel as an unsuccessful attempt to base scientific procedure upon a correspondence between the understanding and experience. If we are to have a rational synthesis of knowledge, it must no more violate the laws of logical thinking (intellect, understanding) than it must ignore the claims of the empirically given. Hence Critical Positivism does not deny the validity of Logic, but makes the following admissions:
a. That the objects of logical thought are unchangeable.
b. That Reality itself is changeable, but that within the changing flux things and relations can be distinguished which change so slowly that they may be treated as logical objects.
c. That the approximate correspondences established between logical objects and unchanging realities admit of progressive correction by the help of deduction and experimental verification, and that in this way new and stricter immutabilities can be arrived at.
Thus to synthesize understanding and reality is to progress towards an exact selection from given realities of those which satisfy the conditions laid down by the logical principles: Reality, that is to say, is already partly rational, and science strives to make it progressively so.