Reader. Your manner of reasoning, [pg 087] 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.
First, the brain is not the measure of the thinking power. The mental capacity of man, and the thinking power of the soul, are not exactly the same thing. The first implies both soul and body, the second regards the soul alone; the first presents to us the musician with his instrument, the second exhibits only the musician himself. The brain is the organ, the soul is the organist. You cannot reasonably pretend that the musical talent, genius, and skill of an organist increase and decrease with the number and quality of the pipes which happen to be in the organ. All you can say is that the musical talent of the organist will have a better chance of a favorable show with a rich rather than with a poor instrument. The organ, therefore, is not the measure of the ability of the organist, and the brain is not the measure of the thinking power. Hence from the fact that the mental capacity of man is enlarged, as you say, in proportion to the material growth of his brain, we have no right to conclude that the thinking principle, the soul, grows with the brain; the right conclusion is that the soul, being in possession of a better instrument, finds itself in better conditions for the exercise of its intrinsic power. The organ is improved and the music is better; but the organist is the same.
Secondly, brain and mind are at present necessarily connected. Does it follow that therefore the soul cannot have a separate existence? By no means. If this conclusion were logical, you might on the same ground affirm also that the body cannot have a separate existence; for the body is as necessarily connected with the soul as the soul is with the body. The reason why your conclusion cannot hold is that the connection of body and soul is necessary only inasmuch as both are indispensable for the constitution of the human nature. But the human nature is not immortal; the soul must quit the body when the organism becomes unfit for the operations of animal life; and therefore the connection of the soul with the body is not absolutely, but only hypothetically, necessary. The soul has its own existence distinct from the existence of the body, for the soul is a substance no less than the body; and therefore it is no less competent to have a separate existence. You deny, I know, that the soul is a substance distinct from the body; but what is the weight of such a denial? What you speculatively deny in your book, you practically admit in the secret of your conscience whenever you say I am. It is not the body that says I; it is the soul: and it is not an accident that perceives self; it is a substance.
Thirdly, the vital power of man, [pg 088] as you say, can manifest its activity only by means of its material organs. This is true; for, so long as the soul is in the body, it must work together with it, according to the axiom, “Every agent acts according as it is in act.” But does the work of the vital power in the material organs warrant your conclusion that the soul needs to be supported by a material substratum? Quite the contrary. For, what needs a material substratum is an accident, and no accident is active; and therefore the vital power, whose activity is manifested in the material organs, is no accident, and therefore needs no material substratum, and, while existing in the material organs, exists no less in itself. Had you considered that the soul, which manifests its activity by means of its material organs, exercises the same activity within itself also, you would have easily discovered that the soul has a being independent of its material organs, and that these organs are the organs of sensibility, not of intelligence.
But I am not going to make a dissertation on the soul, as my object is only to show the inconclusiveness of your reasoning. Your chapter on “Brain and Soul,” with its twenty-eight pages of medical and physiological erudition, offers no proof of your assumption beyond the three sophisms I have refuted. All the rest consists of facts which have not the least bearing on the question. “The whole science of man,” as you say, “is a continuous proof in favor of the connection of brain and mind.” This is what your facts demonstrate; but your object was to show that “the soul is a product of the development of the brain”; and this your facts do not demonstrate, as is evident from your need of resorting to fallacies to make them lie to truth. It is on the strength of such fallacies that you make bold to despise your opponents, forgetting all your shortcomings, and committing a new blunder in the very act of assailing the spiritualistic philosophers. According to you, “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.” You should be ashamed, doctor, of this style of reasoning.
Büchner. Why, if you please?
Reader. Because, first, the connection of brain and mind, as proved by “the whole science of man,” does not authorize you to deny the separate existence of the soul and its substantial independence of the material organs. Secondly, because to call “verbiage” those reasonings which all the great men of all times have, after careful scrutiny, considered as unanswerable, to which they gave their fullest assent, and against which you are incapable of advancing a single argument which has not already been answered by philosophers, is on your part an implicit confession of philosophical ignorance. Thirdly, because it is extremely mean to proclaim your own victory, while you have carefully avoided the combat. You have, in fact, prudently dissembled all the reasons by which the substantiality and spirituality of the human soul are usually proved in psychology; and, to give yourself the appearance of a champion, you have set up a few ridiculous sophisms—as, “the material simplicity of the organs of thought” (p. 125)—to [pg 089] figure as philosophical objections, which they have never been, and never will be; thus reminding us of the great Don Quixote fighting against the wind-mill. Fourthly, because, while boasting of the support which some physiological facts seem to lend to your materialistic theory, you have entirely ignored all those other facts of the intellectual life which were calculated to expose your sophistry and overthrow your conclusions. This is dishonest, doctor; for you cannot plead ignorance in excuse.
Büchner. We proceed from opposite principles, sir; hence we must disagree in our conclusions. It is a law “that mind and brain necessarily determine each other, and that they stand to each other in inseparable causal relations” (p. 139).
Reader. This goes against you; for, if the mind determines the brain, the mind must be a special substance.
Büchner. “As there is no bile without liver, no urine without kidneys, so is there no thought with out a brain. Mental activity is a function of the cerebral substance. This truth is simple, clear, easily supported by facts, and indisputable” (ibid.)