In light of Kant's thoughts about the perception of nature as an organism being a function of our mental wiring the concept of Elan Vital, or an energy that pushes evolution forward, becomes extremely interesting. The idea is that of a vital energy moving evolution forward, of some force inherent in the world that sought realization and that organisms moving and developing help incarnate more and more fully. The transition from simple organisms up through marine life to land life, mammals, and on to man was pictured as being a progressive, preordained, movement that culminates in us. Why the concept came to be is sort of complex, but the virtue of it is that it purported to explain how exactly one species moved into the other. Life presented itself as a sort of fait accompli, as something that had already been accomplished without many links between the species being apparent, with nothing directly suggesting why life moved from one niche in the environment to the other, culminating in human beings.
If we use Kant's idea, the function of elan vital turns into a sort of useful fiction that allows us mentally to comprehend change between established whole states.