The aim of this article is to reconstruct Aristotleś conception of practical reasoning, explanation and understanding of human action. The author examines the problem of practical/theoretical paralelism of reasoning in Aristotle. He describes Aristotleś approach to the problem of function of practical syllogism in explanation of human action. He attempts to show that Aristotleś conception of explanation and understanding of human action is an anticipation of contempory method of humanistical interpretation. This is the method of scientific explanation involving a presupposition of rationality of human being. Explanation of rational action in Aristotle is considerd as an anatomical key to explaining and understanding great variety of types and forms of human action: reasonable and not reasonable (akolatic, acratic), voluntary and non-voluntary, effective and non-effective action.