This article analyses ancient texts to show that ancient philosophical thought was not only considering the practical variants relating to decision-making but it was also constructing a theory of decision-making. The authors propose a reconstruction of the elements of such a theory from a perspective that interprets decision-making as a kind of intellectual activity, which makes it possible to solve a problem without a developed conceptual framework for the decision-making theory (as is the case with Plato's dialogues Gorgias, Theaetetus, and The Republic). It is suggested that the question-answer procedures used by Socrates can be be interpreted as a kind of intellectual activity aimed at decision-making. At the same time, an analysis of Aristotle's texts shows that he discussed decision-making as a special problem on a theoretical level. In the Nicomachean Ethics, Aristotle uses the notion of decision- making explicitly and considers it in the context of such notions as voluntary acts and conscious choice. It is shown that today, as in Antiquity, one can come across different ideas about what decision-making is.