From: Osher Doctorow on
From Osher Doctorow

Since we have obtained from the last few subsections the Cause-
Intersection Optimal P(AB) as:

1) P(AB) = 2P(A) - 1

from P(A-->B) = P(A) (which has optimal "Cause" (A) influence), we
see that:

2) dP(AB)/dP(A) = 2.

Thus, over different A and AB, the optimal rate of change of P(AB)
with respect to P(A) is 2, which is the Mechanical Advantage of a
Simple Moveable Pulley (see Wikipedia's "Mechanical Advantage" online
for example).

Osher Doctorow