Edge Makes the Difference
the tassel hangs freely and covers the border between the halves,
few people can see the difference in the color. It is very subtle.
It is only when the border is exposed that it becomes apparent.
Edges are important in defining what we see. When the rope tail
is lifted, two separate squares become visible, one significantly
darker than the other. When the rope tail coveres the edge, the
two sides are indistinguishable. The two squares are really identical.
There is only a difference at the point where they meetthe
edge. Each square is shaded lighter to darker, from left to right.
In the middle, the dark edge of one square meets the light edge
of the other. The eye concentrates on the boundary and assumes the
rest of the square is the same.