merely within the mind (i.e., they are real in the strictest sense of the word). Indeed, according to the Platonic understanding, the world of Form is--as well as transcendent to the sensible world--the essential basis both thereof, and of true (stable, enduring) knowledge. Conversely, sensible particulars--being changeable, subject-relative, and tied to unreliable perception--provide an apt basis for only opinion.

For example, consider a triangle drawn upon a blackboard: such a triangle, as drawn by a human hand, is necessarily imperfect--as