198. He thus logically cuts off his psychology from the support which, according to popular conceptions, its primary truths derive from physiology. We have already noticed how with Locke metaphysic begs defence of physic; [1] how, having undertaken to answer by the impossible method of self-observation the question as to what consciousness is to itself at its beginning, he in fact tells us what it is to the natural philosopher, who accounts for the production of sensation by the impact of matter ‘on the outward parts, continued to the brain.’ To those, of course, who hold that the only possible theory of knowledge and of the human spirit is physical, it must seem that this was his greatest merit; that, an unmeaning question having been asked, it was the best thing to give an answer which indeed is no answer to the question, but has some elementary truth of its own. According to them, though he may have been wrong in supposing consciousness to be to itself what the physiologist explains it to be--since any supposition at all about it except as a phenomenon, to which certain other phenomena are invariably antecedent, is at best superfluous--he was not wrong in taking the physiological explanation to be the true and sufficient one. To such persons we can but respectfully point out that they have not come in sight of the problem which Locke and his followers, on however false a method, sought to solve; that, however certain may be the correlation between the brain and thought, in the sense that the individual would be incapable of the processes of thought unless he had brain and nerves of a particular sort, yet it is equally certain that every theory of the correlation must presuppose a knowledge of the processes, and leave that knowledge exactly where it was before; that thus their science, valuable like every other science within its own department, takes for granted just what metaphysic, as a theory of knowledge, seeks to explain. When the origin, for instance, of the conception of body or of that of an organic structure is in question, it is in the strictest sense preposterous to be told that body makes the conception of body, and that unless the brain were organic to thought I should not now be thinking. ‘The brain is organic to thought;’ here is a proposition involving conceptions within conceptions--a whole hierarchy of ideas. How am I enabled to re-think these in order, to make my way from the simpler to the more complex, by any iteration or demonstration of the proposition, which no one disputes, or by the most precise examination of the details of the organic structure itself? [1] See above, paragraph 17. Those who think it will don’t understand the question.