Yesterday Jamie and I went to DuPont State Forest. Along the way, I read an excerpt (342c-344d) from Plato's Seventh Letter. In this excerpt the great spiritual master in the guise of philosopher describes how the four (names, descriptions, bodily forms, and concepts) are of "inaccurate character" and make nearly everyone "prey to complete perplexity and uncertainty."
Plato gives the example of a circle to illustrate how we have the name "circle", the description as "the thing which has everywhere the same distances between extremities and its center", the bodily form of a circular object, and, finally, concepts, which may be correct or incorrect.
As a result of the possible shortcomings of the four, Plato taught about the fifth entity. If I understand correctly, following the example of the circle, the fifth is the Idea of the circle. While the four belong to the sensible (or manifest) realm, the fifth belongs to the intelligible realm.
The reason we can know what a circle is, and not get it confused for a square or a triangle, is because the Idea exists within our consciousness. This Idea is not affected in the least by the sensible experience of circles. If all the circles in the world were destroyed the Idea would still exist within consciousness.
At DuPont, Jamie and I saw the spectacular Triple Falls, among others, as I was reflecting on this teaching from Plato.
However beautiful certain things are, a consideration of Ideas leads us into contemplative silence.