The paper aims at reconstructing the fundamentals of the sophistic anthropology. Contrary to the recognized view of the humanistic shift which took place in the sophistic thought, there is evidence that the sophists were continuously concerned with the problems of philosophy of nature. The difference between the sophists and their Presocratic predecessors was that their criticism of the philosophical tradition and the transformative answers given to the old questions were the basis and the starting point of the “ethical” and “rhetorical” part of their intellectual activity. This naturalistic perspective is reflected in their research in the field of medicine and biology, in the discussion about “the human nature”, and in their interest in the individual physiological and mental conditions, which determine the state of the human body and the behaviour of a man. The sophists pioneered in linguistic, rhetorical, and philological studies. To enhance the power of persuasion, they investigated how various mental conditions influenced cognitive processes and physiological reactions. Thus they started a thorough examination of the human psyche, initiating the field of psychology. Although the originality of the sophists in each of the aforementioned aspects is undeniable, a complete picture of the sophists can only be achieved by examining the sources of their thought: the Presocratic philosophical tradition, Hippocratic medicine, and earlier literary tradition.