In the first part of the paper, the author presents in ten theses with a commentary Popper's theory of the objective knowledge and of three worlds, showing its difficulties and vagueness and trying to clarify it. The second part comprises discussion with a few Popper's theses. He especially argues against the thesis about autonomy of the third world, and about epistemology limited to examination of objects from the third world only. In relation to this, the author shows some defects of Popper's argumentation from the 'Objective Knowledge'. The conclusion of the article is a different interpretation and an anew formulation of Popper's theory.