The transformation of empirical knowledge into theoretical one is studied in the article on the basis of four methodological principles: 1) the classical understanding of theoretical knowledge as knowledge about the necessary, understood as necessary; 2) the consequent determinism, according to which every event in the objective world is necessary; 3) the theory of the three worlds, which distinguishes the objective world, the world of knowledge about it and the world of ontology of this knowledge:  4) aposteriorism, which states that theoretical knowledge is not introduced into the empirical from outside, but is derived from it.

In accordance with these principles, empirical knowledge is interpreted as knowledge about the existence of the event under study and its attributes, and theoretical - as knowledge about the necessity of their existence. It is argued that the transformation of empirical knowledge into the theoretical starting points is reduced to removing from the empirical knowledge of obscuring and distorting content. There are three types of this content: congeneric, foreign and subspecific in relation to the subject. The methods of their removing are described. It is shown that as a result of the application of these methods, empirical knowledge becomes necessary, absolutely universal and capable to deductive self-development, i.e. theoretical.