Mowgli and Doctor Doolittle were my friends when I gave up fairy stories. Years later, as an undergraduate I was enabled to unmask them, or rather to site them accurately in the zoo of fantasy, for, so we were taught, while ants and monkeys might live in societies, man alone could be characterized by language and culture. Mowgli as the boy living among wolves, and Doctor Doolittle speaking the language of animals, represented in different ways the craving of fantasy to break through the bonds of necessity, either by sloughing off the second skin of transmitted human knowledge, or by discovering in the animal kingdom the same arbitrary and artificial codes by which we communicate. Lately, Mowgli and Doctor Doolittle have returned to the boundary of my reflections on the cultural and ethical significance of the biological aspect of human personality, perhaps to suggest that their very anomalousness indicates the necessary inadequacy of all attempts to categorize absolutely. Yet they retain the essential innocence of uncommitment, whereas this article is loaded in that not only was its starting point consideration of Humanae Vitae, but also that it leans very heavily to the Pope’s point of view. I shall be concerned mainly with looking at underlying assumptions, rather than trying to synthesize. If the Pope or his critics are relying on principles which the development of the social sciences has shown to be inadequate, it does not automatically follow that the other side is right; but the terms of the debate must be recast.