In this article dialectic is taken to mean that way of considering the development of thought and reality theorized by Hegel and later reconsidered and discussed by Marx; even today the dialectic concept of reality is an important theme in modern Marxism. As for Marx, some people hold that he turned the Hegelian concept of dialectic back to front, shifting its accent and basis from the Idea to real and concrete man, seen in his social relations; but there is no doubt that, thanks to this reversal, or rather thanks to a varied and complex attitude to dialectic (in some ways more positive and more directly fruitful than the Hegelian logical instrument, in others more polemical and detached), Marx never abandoned his determination to preserve its validity even in a context more or less radically different from Hegel's. Although, within the sphere of modern Marxism, beside the more orthodox school of thought that makes the dialectic concept of reality one of its doctrinal bastions, there is also the school that attempts to limit its doctrine to the field of historical reality and the world of man, relinquishing every pretension to a more generalized metaphysical perspective; one must not forget that even the latter does not believe it possible to form an adequate concept of the development of history without any reference to the dialectic concept; whether the whole of reality or only history are considered, it does not seem possible to leave the dialectic theory of development out of a consideration of either point of view.