Since men in their endeavors behave, on the whole, not just instinctively, like the brutes, nor yet like rational citizens of the world according to some agreed-on plan, no history of man conceived according to a plan seems to be possible, as it might be possible to have such a history of bees or beavers. One cannot suppress a certain indignation when one sees men’s actions on the great world-stage and finds, beside the wisdom that appears here and there among individuals, everything in the large woven together from folly, childish vanity, even from childish malice and destructiveness. In the end, one does not know what to think of the human race, so conceited in its gifts. Since the philosopher cannot presuppose any [conscious] individual purpose among men in their great drama, there is no other expedient for him except to try to see if he can discover a natural purpose in this idiotic course of things human. In keeping with this purpose, it might be possible to have a history with a definite natural plan for creatures who have no plan of their own.
We wish to see if we can succeed in finding a clue to such a history; we leave it to Nature to produce the man capable of composing it. Thus Nature produced Kepler, who subjected, in an unexpected way, the eccentric paths of the planets to definite laws; and she produced Newton, who explained these laws by a universal natural cause.
All natural capacities of a creature are destined to evolve completely to their natural end.
Observation of both the outward form and inward structure of all animals confirms this of them. An organ that is of no use, an arrangement that does not achieve its purpose, are contradictions in the teleological theory of nature. If we give up this fundamental principle, we no longer have a lawful but an aimless course of nature, and blind chance takes the place of the guiding thread of reason.
In man (as the only rational creature on earth) those natural capacities which are directed to the use of his reason are to be fully developed only in the race, not in the individual.