Take the breeder of pigeons. Out of the blue rock pigeon he develops the pouter or the fan-tail; he chooses out, generation after generation, the forms that show most strongly the peculiarity that he wishes to develop. He mates such birds together, takes every favouring circumstance into consideration and selects again and again, and so on and on, till the peculiarity that he wants to establish has become a well-marked feature. Remove his controlling intelligence, leave the birds to themselves, and they revert to the ancestral type.
Or take the case of the gardener. Out of the wild rose of the hedge has been evolved every rose of the garden. Many-petalled roses are but the result of the scientific culture of the five-petalled rose of the hedgerow, the wild product of nature. A gardener who chooses the pollen from one plant and places it on the carpers of another is simply doing deliberately what is done every day by the bee and the fly. But he chooses his plants, and he chooses those that have the qualities he wants intensified, and from those again he chooses those that show the desired qualities still more clearly, until he has produced a flower so different from the original stock that only by tracing it back can you tell the stock whence it sprang.
So is it in the application of the laws of psychology that we call Yoga. Systematized knowledge of the unfolding of consciousness applied to the individualized Self, that is Yoga. As I have just said, it is by the world that consciousness has been unfolded, and the world is admirably planned by the logos for this unfolding of consciousness; hence the would-be yogi, choosing out his objects and applying his laws, finds in the world exactly the things he wants to make his practice of Yoga real, a vital thing, a quickening process for the knowledge of the Self. There are many laws. You can choose those which you require, you can evade those you do not require, you can utilize those you need, and thus you can bring about the result that nature, without that application of human intelligence, cannot so swiftly effect.