Let me further illustrate this point by an allusion to the electric telegraph, by means of which ideas and words are transmitted from mind to mind with a rapidity to which ordinary language cannot attain. Now, the electrical battery may be not inaptly compared to the brain, and the telegraph wires to the nerves which emanate from it. If the battery be out of order, or the telegraph wires be broken, this lightning language, by which mind speaks to mind, becomes impossible. In the same way, idiocy may be considered as a disease of the instrument rather than of the performer; the idiot's brain is damaged and has become an unfit instrument for the outward manifestation of the powers of the mind, but the lowest idiot possesses the germs of intellectual activity and moral responsibility; and within his malconstructed organism, there lies concealed in its fragile, fleshly casket, a precious jewel of immortality--an imperishable essence that is destined to live on for ever and for aye, through countless æons of time, when the dicta of these dreamers of whom I have been speaking, to use the language of one of them, "shall have melted away like streaks of morning cloud into the infinite azure of the past." I repeat it, we must take care not to confound the organ with the person who possesses this organ: the eye is not that which sees, it is only the organ by which we see; the ear is not that which hears, it is only the organ by which we hear. Precisely in the same way and in the same sense, the brain is the organ of mind, the organ by which our mental faculties become _externally_ manifested. That it cannot be otherwise is shewn by the results of memory. The brain is of a perishable nature, its atoms are constantly changing; the body is continually throwing off old particles and appropriating new ones, every breath that is drawn, and every exertion that is made, cause some minute change in the bodily frame-work, so that it is never entirely the same;[34] there is no person, therefore, who has the same brain that he had 20 years ago; and the vivid impressions of the past are utterly inexplicable on the supposition that mental activity is a mere function of any perishable organ like the brain, but they necessitate the conclusion that mind and body, spirit and matter, are two entirely heterogeneous substances, and that mind--the concrete _Ego_--is independent of the material organ by which its external manifestation is alone possible.[35] However tempting it might be, I feel I must not trespass any further by dwelling on the mysterious connection between matter and mind, a subject the complete comprehension of which is beyond the limits of our finite capacities. As Goethe philosophically remarks, "We are eternally in contact with problems. Man is an obscure being, he knows little of the world, and of himself least of all."