3. Constancy and Equality Compared
Compare and contrast:
(x = y) = For any property P, P(x) iff P(y).
Con(P) = For any objects x and y, P(x) iff P(y).
Equality and constancy are complementary. Both start from objects having a property equally; equality generalizes the property, constancy generalizes the objects. Equality defines entities; constancy defines laws.
Their negations are also similar:
(x y) = For some property P, P(x) xor P(y).
Var(P) = For some objects x and y, P(x) xor P(y).