p In the process of cognising objective reality, people form concepts, through which they express and record the reflected properties and connections of the objects and phenomena of the surrounding world and which are ideal images of these objects and phenomena. Concepts reflecting the most essential and fundamental aspects and connections in a field of phenomena are called categories. Each science has its own categories. The categories of political economy, for instance, are: commodity, money, value, surplus value, labour force, profit, etc.; the categories of biology are: organism, medium, assimilation, dissimilation, heredity, species, genus, etc.; the categories of juridical science are: law, legal norm, act, legal relation, legal offence, etc. Philosophy, tgr>. T^g it* ^at-ggr> ries. As distinct from the categories of special ’sciences, philosophical categories reflect not merely the most essential properties and connections, but universal properties and connections, i.e. those inherent in all the phenomena of reality and knowledge. Philosophical categories are universal concepts applicable to any field of reality. They include, for instance, such concepts as the 176 individual and the general, quantity and quality, cause and effect, content and form, necessity and accident (chance), law, essence and phenomenon, and contradiction.

p Categories did not all appear simultaneously in the course of history. Each of them is connected with an absolutely definite stage in the development of knowledge. Categories record the universal aspects and relations revealed at a certain stage of development, and reflect the peculiarities of this stage, being support points that enabled man to rise above nature. In other words, categories that reflect the universal aspects and connections of the outside world are, at the same time, stages in the development of knowledge, moments marking the passage of knowledge from one stage to another. Lenin wrote: “Man is confronted with a web of natural phenomena. Instinctive man, the savage, does not distinguish himself from nature. Conscious man does distinguish, categories are stages of distinguishing, i.e. of congnising the world. ...”  [176•1 

p Besides, the categories of dialectics are also forms of thinking. They serve as a medium for comprehending the actual material obtained in the course of scientific research and the practical transformation of reality. The most essential characteristics of an object are revealed during the mental processing of scientific data. Specifically, when we examine data in the light of the categories of the general and the particular, we 177 establish the identity and distinctions of the object we are studying in comparison to other objects; when we view them in the light of the categories of causality and necessity, we establish the object’s causal dependence and its necessary and accidental aspects and connections; and when we analyse them from the standpoint of the categories of quantity and quality, we discover the object’s quantitative and qualitative characteristics and under certain conditions also their interrelationship.

Since categories reflect and record the universal aspects and connections of reality, i.e. the universal forms of being, they make up the content of dialectics; since they are also the points of departure or stages in the process of cognition, they are part of the theory of knowledge; moreover, since they are forms of thinking, they are objects ot study for dialectical logic.