_Their Differences――The Development of the Meaning of Idea._ 1. But the forms or ideas are so vitally different in the doctrines of these two philosophers that they have nothing in common save the name. On the one hand, Democritus took the word “idea” just as he found it in popular speech. It is the shape of a visible thing, the geometrical form of physical objects. It gets no new content in his hands, but is merely the physical atom. With Plato, however, the word gets a new meaning. He fills the form or idea with an ethical content. The idea as a quantity becomes now a quality. The idea becomes an Idea. The forms of Plato are logical species and teleological causes, while the forms of Democritus are atom-complexes.[23] In both philosophers they are the norms of reality. But while Democritus still keeps his forms as the realities of physical nature, Plato conceives his forms to be true realities of objective human nature. 2. This vital difference between the two philosophers may get some explanation from the difference in the philosophical inheritance of each. To be sure, they were contemporaries, both being born in the Anthropological Period and both doing their most mature work in the Systematic Period. Both, too, were acquainted with the philosophy of the preceding time. But the ethical teaching of Socrates dominated Plato, and through it he became the legitimate perfecter of the Greek enlightenment and the anthropological movement. But what was the influence of Socrates upon Democritus? It seems to have been nothing. Why is Plato absolutely silent about Democritus when he mentions other Greek philosophers? No one has yet been able to say. Democritus stands at Abdera isolated from the ethical movement at Athens. The only influence upon him from that movement came from Protagoras, who was a member of the school at Abdera. Democritus is the finisher of the Cosmological movement.