_Büchner._ Yet “the mental capacity of man is enlarged in proportion to the material growth of his brain, and is diminished according to the diminution of its substance in old age” (p. 110). “It is a fact known to everybody, that the intelligence diminishes with increasing age, and that old people become childish.... The soul of the child becomes developed in the same degree as the material organization of its brain becomes more perfect” (p. 111). “Pathology furnishes us with an abundance of striking facts, and teaches us that no part of the brain exercising the function of thought can be materially injured without producing a corresponding mental disturbance” (p. 119). “The law that brain and soul are necessarily connected, and that the material expansion, shape, and quality of the former stands in exact proportion to the intensity of the mental functions, is strict and irrefutable, and the mind, again, exercises an essential influence on the growth and development of its organ, so that it increases in size and power just in the same manner as any muscle is strengthened by exercise” (p. 122). “The whole science of man is a continuous proof in favor of the connection of brain and mind; and all the verbiage of philosophical psychologists in regard to the separate existence of the soul, and its independence of its material organ, is without the least value in opposition to the power of facts. We can find no exaggeration in what Friedreich, a well‐known writer on psychology, says on this point: ‘The exhibition of power cannot be imagined without a material substratum. The vital power of man can only manifest its activity by means of its material organs. In proportion as the organs are manifold, so will be the phenomena of vital power, and they will vary according to the varied construction of the material substratum. Hence, mental function is a peculiar manifestation of vital power, determined by the peculiar construction of cerebral matter. The same power which digests by means of the stomach, thinks by means of the brain’ ” (pp. 124, 125). _Reader._ Your manner of reasoning, doctor, is not calculated to bring conviction, as every one of your arguments contains a fallacy. Your first argument is: The brain is the measure of the thinking power; and therefore the thinking power, or the soul, is a result of organic development. The second is: Brain and mind are necessarily connected; and therefore the soul cannot have a separate existence. The third is: The vital power of man can only manifest its activity by means of its material organs; and therefore the soul needs to be supported by a material substratum. Such substantially is the drift of your argumentation. Now, I maintain that the three arguments are merely three sophisms.