I. Haeckel and His Opponents

When we raise the question as to the origin of species in its most important form, in that which concerns the origin of man, there are only two answers possible. Either a consciousness endowed with reason is not present prior to its actual appearance in the world, but evolves as the outcome of the nervous system concentrated in the brain; or else an all-dominating world-reason exists before all other beings, and so shapes matter that in man its own image comes into being. Haeckel (in Monism as the Link between Religion and Science, p. 21) describes the becoming of the human mind as follows: “As our human body has slowly and step by step built itself up from a long series of vertebrate ancestors, so the same thing holds good of our soul: as a function of our brain it has developed itself step by step in interaction with that organ. What we term for short the ‘human soul’ is indeed only the sum-total of our feeling, willing, and thinking—the sum-total of physiological functions whose elementary organs consist of the microscopic ganglionic cells of our brain. Comparative anatomy and ontogeny show us how the marvellous structure of the latter, of our human soul-organ, has built itself upwards gradually in the course of millions of years out of the brain-forms of the higher and lower vertebrates; while comparative psychology shows us how, hand in hand therewith, the very soul itself—as a function of the brain—has evolved itself. The latter shows us also how a lower form of soul activity is already present in the lowest animals, in the unicellular protozoa, infusoria, and rhizopods. Every scientist who, like myself, has observed through long years the life-activity of these unicellular protista, is positively convinced that they also possess a soul; this ‘cell-soul,’ too, consists of a sum of feelings, representations, and volitions; the feeling, thinking, and willing of our human soul is only different therefrom in degree.”