If one were to ask for a statement of the essence of Professor Popper's contribution to the theory of scientific research, it could probably best be expressed in the sentence: "Science is a part of the search for truth." We may say then that in fundamental questions, it is always necessary to approach the object of our studies obliquely, by implication rather than by positive assertions and definite conclusions, so that the positivist goal of trying to state precisely what is happening is never appropriate in a really deep problem. And no problem can be deeper than that of what is meant by understanding. With the coming of understanding, then, there is (at least in the field under discussion) what amounts to a revolutionary change in the mode of thinking, in which the earlier associative thought about this field is set aside, and in which the field is comprehended as a totality.