Partial interruptions of physical manifestations of consciousness well illustrate this: as, for instance, when speech-centres of the brain alone are affected. If in such case we had to depend on mouth-muscle alone we should say that consciousness had departed, and might even think that it was non-existent; but the arm-muscle may remain under brain control, and by intelligent writing can show that consciousness is there all the time, and that it is only inhibited from one of the specially easy modes of manifestation. In some cases the inhibition may be complete,--from such cases we do not learn much; but when it is only partial we learn a good deal. I quote again from Dr. Mott, omitting for brevity the detailed description of certain surgical war-cases, under his care, which precedes the following explanatory interjection and summary:-- "Why should these men, whose silent thoughts are perfect, be unable to speak? They comprehend all that is said to them unless they are deaf; but it is quite clear that [even] in these cases their internal language is unaffected, for they are able to express their thoughts and judgments perfectly well by writing, even if they are deaf. The mutism is therefore not due to an intellectual defect, nor is it due to volitional inhibition of language in silent thought. Hearing, the primary incitation to vocalisation and speech, is usually unaffected, yet they are unable to speak; they cannot even whisper, cough, whistle, or laugh aloud. Many who are unable to speak voluntarily yet call out in their dreams expressions they have used in trench warfare and battle. Sometimes this is followed by return of speech, but more often not. One man continually shouted out in his sleep, but he did not recover voluntary speech or power of phonation till eight months after admission to the hospital for shell-shock." Very well, all this interesting experience serves among other things to illustrate our simple but occasionally overlooked thesis. For it is through physical phenomena that normally we apprehend, here and now; and it is by aid of physical phenomena that we convey to others our wishes, our impressions, our ideas, and our memories. Dislocate the physical from the psychical, and communication ceases. Restore the connexion, in however imperfect a form, and once more incipient communication may become possible again. That is the rationale of the process of human intercourse. Do we understand it? No. Do we understand even how our own mind operates on our own body? No. We know for a fact that it does.