We know that there is no abstract truth, that truth is always concrete. And that does not mean at all that only the sensually perceived image, the contemplation of an individual thing may be true. A logically coherent system of definitions is precisely that 'natural' form in which concrete truth is realised in thought. In other words, the concrete is realised in thinking through the abstract, through its own opposite, and it is impossible without it. But that is, in general, the rule rather than an exception in dialectics.
Necessity is in just the same kind of relation with chance, essence with appearance, and so on.
On the other hand, each of the numerous definitions forming part of the conceptual system of a concrete science, loses its abstract character in it, being filled with the sense and meaning of all the other definitions connected with it. Separate abstract definitions mutually complement each other, so that the abstractness of each of them, taken separately, is overcome. In short, herein lies the dialectics of the relation of the abstract to the concrete in thinking which reflects the concrete in reality. The dialectics of the abstract and the concrete in the course of theoretical processing of the material of living contemplation, in processing the results of contemplation and notions in terms of concepts is the subject-matter of study in the present work. Of course, we cannot claim to offer an exhaustive solution to the problem of the abstract and the concrete at all the stages of the process of cognition in general, in all forms of reflection.