I. Haeckel and His Opponents

This great number of germs is confronted with but a comparatively small amount of food and space, the result of this being a universal struggle for existence among organic beings. Only the fit survive and fructify; the unfit have to go under. The fittest, however, will be those who have adapted themselves in the best possible way to the surrounding conditions of life. The absolutely unintentional, and yet—from natural causes—necessary, struggle for existence brings in its train the same results as are attained by the intelligence of the breeder with his cultivated organisms: he creates purposeful ( useful) organic forms. This, broadly sketched, is the meaning of Darwin's theory of natural selection in the struggle for existence; or, otherwise, the “selective theory.” By this theory, that which Kant held to be impossible is reached: the thinking out in all its possibilities of a predetermined form in the animal and vegetable kingdom, without assuming the Universal Mother to be dowered with an organism directly productive of all these creatures.