what old philosophers call “the idea”

You have spoken of “first patterns”- of images without existence save in the soul of the carver, but which he transmutes into matter, making them visible. So that before long such a carver’s shapes can be seen, and so obtain their formal reality, they are there already as forms within his soul. And this same “first pattern” -this shape- is to a hair, what old philosophers call “the idea”.
~ Hermann Hesse ‘Narziss and Goldmund’