3. In the case of twin birth among human beings how can we make out the Reason-Principles to be different; and still more when we turn to the animals and especially those with litters?
Where the young are precisely alike, there is one Reason-Principle.
But this would mean that after all there are not as many Reason Principles as separate beings?
As many as there are of differing beings, differing by something more than a mere failure in complete reproduction of their Idea.
And why may not this [sharing of archetype] occur also in beings untouched by differentiation, if indeed there be any such?
A craftsman even in constructing an object identical with a model must envisage that identity in a mental differentiation enabling him to make a second thing by bringing in some difference side by side with the identity: similarly in nature, where the thing comes about not by reasoning but in sole virtue of Reason-Principles, that differentiation must be included in the archetypal idea, though it is not in our power to perceive the difference.
The consideration of Quantity brings the same result: