If we look at the stage of history we see scattered and occasional indications of wisdom, but the general sum of men's actions is "a web of folly, childish vanity, and often even of the idlest wickedness and spirit of destruction." The problem for the philosopher is to discover a meaning in this senseless current of human actions, so that the history of creatures who pursue no plan of their own may yet admit of a systematic form.

The clew to this form is supplied by the predispositions of human nature.
I have stated this problem almost in Kant's words, and as he might have stated it if he had not introduced the conception of final causes.

His use of the postulate of final causes without justifying it is a defect in his essay.

He identifies what he well calls a stream of tendency with "a natural purpose." He makes no attempt to show that the succession of events is such that it cannot be explained without the postulate of a purpose.

His solution of the problem is governed by this conception of finality, and by the unwarranted assumption that nature does nothing in vain.
He lays down that all the tendencies to which any creature is predisposed by its nature must in the end be developed perfectly and agreeably to their final purpose.