What is the difference between "concepts" in formal logic and concepts in dialectical Logic?

Ilyenkov (1974: 183 - 184) points out that: "the old logic considered every kind of idea or notion whatsoever, insofar as it was expressed in speech or in a term, that is to say, the image of intuition or contemplation held in consciousness by means of speech, which recorded it. As a result, too, the old logic embraced the concept itself only from the aspect from which it was really not distinguished in any way from any notion or intuitive image expressed in speech, from the aspect of the abstract and general, which was really just as common to the concept as to the notion. Thus it came about that it took the form of abstract identity or abstract universality for the specific form of the concept, and could therefore only raise the law of identity and the principle of contradiction in determinations to the rank of absolute, fundamental criteria of the thought-form in general.


Kant also took that stand, understanding by concept any general notion insofar as it was fixed by a term. Hence his definition: ‘The concept is... a general image or representation of that which is common to many objects, consequently a general idea, provided that it can be included in several objects.’


The concept of concept in Dialectical Logic aims to represent the understanding of the essence of the matter, as explained by Ilyenkov: Hegel himself required a more profound solution of the problem of the concept and of thinking in concepts from logic. For him a concept was primarily a synonym for realunderstanding of the essence of the matter and not simply an expression of something general, of some identity of the objects of intuition. A concept disclosed the real nature of a thing and not its similarity with other things; and not only should it express the abstract generality of its object (that was only one of the moments of a concept, relating it to notion), but also the special nature or peculiarity of the object.


Hegel distinguished clearly between universality, which dialectically contained the whole richness of the particular and the singular within itself and in its determinations, and the simple abstract generality, identicalness, of all the single objects of a given kind. The universal concept expressed itself the actual law of the origin, development, and fading or disappearance of single things. And that was already quite another angle on the concept, much truer and deeper, because, as Hegel demonstrated with a mass of examples, the real law (the immanent nature of the single thing) did not always appear on the surface of phenomena in the form of a simple identicalness, of a common sign or attribute, or in the form of identity. If that were so there would be no need for any theoretical science. The job of thought was not limited to empirically registering common attributes.