Plato's Theory of Ideas

in the classification of concepts, which initially seems to concern the scope, εἶδος is used almost always, and only exceptionally, perhaps for the sake of variety, is ἰδέα used; while the unity of the conceptual content is regularly designated as the "one idea" (μία or μία τις ἰδέα), and much more rarely as the one eidos. This unity is also repeatedly described as arising only within the comprehensive glance, the "synopsis" of the mind. Thus, the generation of the unity of thought is still alive in this word, whereas eidos expresses more the finished product, the already given, fixed inner shape of the object.

It is from this modest question regarding the concept that Plato's logical research began. And in his presumably earliest writings, it seems almost limited to this. In this respect, these writings faithfully preserve the character of the Socratic dialogues. For this was the regular course of discussion in these simplest accounts of Socratic conversations, a course the strange man forced everyone he happened to be with to enter: "You praise certain objects as beautiful, you commend certain deeds as brave, a certain demeanor as temperate; you praise Protagoras and others as outstandingly educated and masters of education; you name as the object of rhetoric: deciding on justice and injustice, and so forth. Well then, teach me—for you seem to, and imagine yourself and others to know it—: what is 'the' beautiful, 'the' brave, 'the' temperate, or beauty, bravery, temperance; what is education, what is right, justice, and their opposites?" Regularly, it then turns out that the person questioned cannot provide an account of this, but must shamefully confess that he did not know what he was actually saying when he confidently dispensed these predicates, which were generally related to practical matters. However, one soon senses in these Platonic accounts that while the author has a strong interest in the content of the questions debated—the problems of the moral, of the practically lawful—at the same time, often even in the first place, the formal aspect also forms the object of his attention: the general requirements for a tenable conceptual definition and the laws of logical discussion and sufficient argumentation. It is the discovery, indeed it is the very birth of the concept of the logical, that one overhears in these conversations, or rather, participates in their pains and joys oneself.