In the face of all this scorn I boldly affirm that mental philosophy is not exploded, and that it never will be exploded.Whatever men may profess or affect, they cannot, in fact, do without it.It often happens that a profession of contempt for all metaphysics, as being futile and unintelligible, is often an introduction to a discussion which is metaphysical without the parties knowing it (just as the person in the French play had spoken prose all his life without being aware of it); and of such metaphysics it will commonly be found that they, are futile and unintelligible enough.Often is Aristotle denounced in language borrowed from himself, and the schoolmen are disparaged by those who are all the while using distinctions Which they have cut with sharp chisel in the rock, never to be effaced.There are persons speaking with contempt of Plato, Descartes, Locke, and all the metaphysicians, who are taking advantage of the great truths which they have discovered.Perhaps these individuals are telling you very solemnly that they prefer the <practical> to the <theoretical>, or that they care little for the <form> if they have the <matter>, and are profoundly ignorant that they are all the while using distinctions introduced by the Stagyrite, and elaborated into their present shape by the scholastics.But surely, they will tell you, the discovery of a new <species> of an old <genus> is a more important event than all your philosophic discoveries; and they will be surprised to learn that we owe the introduction of the phrases genus and species to Plato or to Socrates.Or perhaps they boast that they can have <ideas> without the aid of the philosophers, forgetting that Plato gave us the word <idea>, while Descartes and Locke brought it to its present signification."Ah, but," says our novel reader, eager to discover whether the heroine so sad and forlorn in the second volume is to fall in with her lover, and be married to him before the close of the third, "metaphysics are associated in my mind with a dreary desert without and a headache within; " and is quite unaware that he is able so to express himself, because philosophers have explained that ideas are <associated>.I could easily show that in our very sermons from the pulpit, and orations in the senate, and pleadings at the bar, principles are ever and anon appealed to which have come from the heads of our deepest thinkers in ages long gone by, and who may now be forgotten by all but a few antiquarians {457} in philosophy.Our very natural science, in the hands of such men as Faraday and Mayer, is ever touching on the borders of metaphysics, and compelling our physicists to rest on certain fundamental convictions as to extension and force.The truth is, in very proportion as material science advances, do thinking minds feel the need of something to go down deeper and mount up higher than the senses can do; of some means of settling those questions which the mind is ever putting in regard to the soul, and the relation of the universe to God; and of a foundation on which the understanding can ultimately and confidently repose.
II.Metaphysics may have now to take anew start by taking advantage of physiological research.The Scottish school has never been slow to profit by the discoveries of science as to the brain, the nerves, the senses.From the first, and all along, they embraced and used all that was established in regard to the eye not being originally percipient of distance, to the distinction between the nerves of sensation, and to the reflex system in the human body; and they set themselves against premature and rash hypotheses by Hartley, by Erasmus Darwin, and by the phrenologists.But physiology in its natural and necessary progress is coming nearer and closer to the line which divides mind from matter, and in these circumstances mental science has both to watch and profit by the investigations which are being so diligently pursued.
First, metaphysics must restrain the rash inferences of mere physiologists, as Reid did the vibration theory of Hartley, as Brown did the hypotheses of Darwin as to life, and as Hamilton did the pretended science of craniology.
They must make the whole educated community know, believe, and realize, that such physical actions as attraction, repulsion, and motion are one set of phenomena, and perception, reasoning, desire, and moral discernment another and a very different set of phenomena.We can trace so far into the brain what takes place when the mother sees her son thrown out from a boat on the wild waves; we can follow the rays of light through the eye on to the retina, to the sensorium, possibly on to the gray matter in the periphery of the brain; and in the end physiology may throw some light on the whole cerebral action.But in the end, as at the beginning, we are in the domain of matter and {458} motion;we have only the same action as takes place in the brain of the dog as it looks on.But when the mother's affection rises up, when she forgets herself in thinking of her boy, when she uses expedients for rescuing him, when she resolves to plunge into the water and buffets the billows till she clasps her boy and lavishes her affection on him, we are in a region beyond that reached by the physiologist,-- a region which I believe he can never reach; and it is of importance to tell him so.But the psychologist can reach that region by consciousness, and ought diligently to explore it.