This essay is a logico?philosophical critique of the Marxian system of sociology with special reference to the theory of social change. To every change in the natural order (taken in conjunction with the technological order) corresponds an appropriate change in the human order, that is, in the system of social relations. This, it is shown, is the fundamental Marxian thesis regarding social equilibrium. And accordingly the key idea regarding social change is that a gradually maturing inherent disproportion between the two (...) orders is the basic condition of social change, eventually leading to the establishment of a new social equilibrium at a higher level. A close examination of the concept of mode of production and changes therein is attempted in the course of elucidating the above thesis. It is argued that the technological interpretation of the concept of mode of production conflicts with the Marxian anthropology and that we should have a structural interpretation according to which it will refer to the economy as a whole and will include among other elements production relations. This interpretation leads the discussion into one of the central problems of Marxism, namely, the relation between the mode of production and the social system. It is argued that the social system is basic to Marx and after a close analysis of the concept of system it is shown that the Marxian theory of base and superstructure rests mainly on confusion of conceptual orientations. This, it is shown, is connected with a fundamental idea of Marxism, viz., that of a system without a transcendent centre. This essay endeavours to prove that such an idea is logically untenable. Hence the Marxian Laws of Transformation of Quantity into Quality and Negation of Negation are examined and shown logically untenable. The last section discusses the question about the determinant of technological change and eventually of social change. Three possible Marxian solutions are examined: (a) in terms of needs ? it is argued that this is inconsistent with Marx's theory of man and labour; (b) in terms of science and new ideas ? it is shown that this ultimately goes contrary to Marxian materialism and positivism; and finally, (c) the systemic solution in terms of the dialectic of nature and man is subjected to logical scrutiny and it is shown that this cannot be consistent and valid without involving a trans?historical standpoint; for, it is argued, the idea of the self?directing Humanity on which it rests is a self?contradictory notion. (shrink)