DIALECTICAL COKtRADICTION IN THE SCIENCES 59 Such a Star is called a black hole. Slack holes would continue to exert gravitational attraction on other bodies but would not emit any light or energy. Black hole^, according to the pffesent theory, would have no contradictory motion and its only motion would be tbi iliv^ard mechanical motion of all its parts. Black holes have not been spotted so far. They may be spotted in the future. Bin a ^reat amount ot qualitative study of it§ move^-ment and development is called for before we apply the quantitative ff^ld equations of Eitistein to these conditions. Einstein'^ field equations are derived from the fact thai the gravitational power bf attraction of a body (gravitational mass) ^nd the measure of th6 response to forces of the same body (inertial mass) are equal. Thi^ principle of equivalence has been observed in a wide variety of situations. Einstein's revolutionary theory succeeded in uniting these opposites of attracting mass and responding mass, just as Marx*^ analysis of the concept of value united the opposites of relative value a^d equivalent value But the unity of opposites is relative, temped rary; it is their clash which is absolute. The unity of opposite^ in t&e concept of value i^ seen in its clash in the economic crises of capitalism, and the, clash only ceases when the system of socialism i& established when the law of value itself undergoes a change. In the same way, it does not follow that the equality of inertial fnass and gravitational mass which is observed in classical conditions should hold under the conditions within the interior of a star having a density of the order <^f a niiltion million grams per cubic cou Quantum conditions would have to be taken into account at thfe stage. The existence of trapped surfaces and singularities in thA space-time geometries of general relativity shows that all is not wifll with the description of gravitation by general relativity. ? It has been shown that such trapped surfaces exist evep Wll^ft the densities are not necessarily high if we take the usual Eiiistelft interpretation of gravity as curvature of the space-time manifold* Iti fact the very concept of a manifold used in relativity may not be applicable in studying the structure of stellar collapse at this stage. The plisent approach is to start with the manifold structure described by the field equations and then to describe the motions as geode^te curves in this structure. Everything according to this approach is geometry. Now Alexandrov has shown how the geometrical structure is itself obtained by the physical processes. Using the physical processes, c,ause-effect relations in material motion, a geometry can be constructed (Alexandrov topology). Thus it is 'the motion that we have to study first, and thefi talk of the geometrical structures. This brings us back to the need to study qualitatively the properties of black holes bbfore we give quantitative laws. This is an example of quality going into quantity. We can then expect internal contradictory aspects within the black holes as well. This is what dialectics suggests.