Middle term, reason, and the formal cause

The article deals with Aristotle's doctrine of syllogism as an elementary form of proof. According to Aristotle, of all fourteen valid syllogism forms, the first form of the first figure is best suited for this task, since its conclusion is "general and affirmative." But Aristotle also considers a special case of this syllogism form, when both terms of the first premise are equal, and its converse goes without restriction. Aristotle shows that in this case, on purely logical grounds, it is impossible to distinguish middle term from major, since they are interchangeable. Therefore, such syllogisms turn out to be ambiguous and do not prove anything. What is to be done? Aristotle turns to epistemological grounds to make the definition converse impossible and thus to get the ability to state it as the major syllogism premise. He claims that knowledge of the formal cause of a thing leads to the knowledge of a thing itself, but not vice versa. A determinable requires clarification with the help of the determinant, and not on the contrary. Therefore, the formal cause of a thing by Aristotle is always the cause, and not the thing itself, or the action. Therefore, if the definition serves as a major premise of the syllogism, then the formal cause of a thing always turns out to be a middle term, while for the major premise stands the thing itself. Thus, the interchangeability of terms is disestablished, since, as Aristotle says, the cause has the first place in comparison with its effect. As a result, a syllogism becomes complete, unambiguous, and quite “usable”.