Every man must be free to accept, or reject, the Covenant, even though we think him insane! The structural differential is a physical chart or three-dimensional model illustrating the abstracting processes of the human nervous system. In one form, it appears as a pegboard with tags. Created by Alfred Korzybski , and awarded a U. The device is intended to show that human "knowledge" of, or acquaintance with, anything is partial—not total.