Led you to Duncan.

But the stage direction must be taken as a literal appearance of the ghost, so as to make it visible to the audience, while it is invisible to all at the table excepting Macbeth himself.

If, now, we go forward to the night when Lady Macbeth is walking in her sleep, and remember what had occurred previous to and at the banquet, we see how, without any actual previous knowledge that her husband intended to have Banquo killed, and with only the surmise that he had been killed, which comes to her at the banquet, she came to say to her husband, in her dream:

I tell you yet again, Banquo's buried; he can not come out of his grave.

Here we have a fact lodged in the mind during the waking hours, and in sleep wrought into a strange mixture with the killing of Duncan, with which it had in reality no connection, having transpired afterward. This is very strong proof of the capacity of the mind to act during sleep without the action of the brain. The mind of the guilty sleep-walker is filled with horrible memories, which it can not shut out, but with which it can not deal in their actual order and true relations, because the sequences of thought, during sleep, are abnormal. Those whose experience has never involved any such workings of conscience are perfectly aware of the fact that in dreams ideas that are separately lodged in the consciousness become entangled with each other in the most fantastic manner. Lady Macbeth at one moment even thinks of herself as if she were some one else, and asks, Where is the woman now who was the wife of the thane of Fife? Every one has experienced in sleep the same projection of one's self out of one's own consciousness; so that we seem to be contemplating ourselves as if we were a different person.

The phenomena that occur during the delirium of fever, where the normal consciousness is lost for the time being, are in some respects analogous to and in some respects different from those which occur during the somnambulistic condition. Delirium occurs when the body and the brain are not in the condition of sleep; but the senses of perception convey false impressions to the mind, and the mind itself has temporarily lost its power of correcting its own action by its former experience. The nearest friends who are around the bedside are not recognized by the sufferer; they appear to be strangers, and the patient talks to them as if both they and he were not their real selves. It would seem that we can safely infer from the state of delirium a suspension of the direct and normal connection between the brain and the mind; that neither of them can act, in relation to the other, as they both act when there is no such disturbance: but that this condition, so far from proving or tending to prove that the mind is not an independent spiritual existence, has a strong tendency to prove that it is. Insanity, on the other hand, is probably a derangement of the mental organism akin to derangement of the physical organism, but not necessarily connected with or induced by the latter, for the bodily health of the insane is often entirely sound while the mind is in an entirely unsound and irrational condition. But the phenomena of insanity are too various and multiform, and too much dependent on both physical and moral causes, to afford any satisfactory proofs of the postulate which I propound in this essay. The safest line of investigation is that which I suggested in the first instance, namely, to regard the mind as an organism, and to ascertain whether it is susceptible of anatomical examination in a sense analogous to anatomical examination of the bodily organism. All that I have hitherto said is useful by way of preliminary illustration of my main hypothesis. It has a strong tendency to show that the mind, instead of consisting, as some philosophers now suppose, of the products of a material organism, is itself an organized being with a definite structure and capable of living a life of its own, although at present dwelling in a corporeal organism which affects it in various ways while the connection lasts. The theory that all mental phenomena are products of our corporeal organism is one that appears to derive great support from examinations of the structure of the brain and of the whole nervous system. The physical anatomy of man exhibits very striking illustrations of the influence of corporeal changes upon the mental state, as the mental changes show corresponding influences upon the corporeal state. But, then, there are undoubtedly phenomena that are purely and exclusively mental; and therefore when we undertake to solve these mental phenomena by the materialistic hypothesis we find a sense of inadequate causation confronting us so directly that we are compelled to look for a solution elsewhere. It is certain that things take place in the inner recesses of our minds, in the production of which the bodily senses not only render no aid, but in which they have no part whatever. It is necessary, therefore, to carry our investigations into a class of mental phenomena in which all physical causation ceases to afford an adequate guide to a conclusion.

It will not be denied that the products of material organisms can be proved to consist of matter and of nothing else. Their presence can be detected by some physical test. For example, if it be true that all animals have been evolved from protoplasm, the organisms are simply changes in the form of a certain portion of matter. If, in an individual organism having a highly developed nervous structure, there are actions produced by an excitation of the nerves of sensation, those actions are simply molecular changes in the matter comprising the sensitive and easily moved substance of the nerve-fibers. However far and into whatever minutiæ we carry our investigations into organized matter, we find that its products remain material, and that they consist only of changes in the material substance of a material organization. But, when we pass from such material products into the domain of purely mental phenomena, are we warranted in saying that, although the latter are not, properly speaking, products of the material organization, they are effects corresponding to and dependent upon the excitation of the nerves of sensation? This last hypothesis must assume one of two things: either that there is a distinction between those corporeal feelings which do not and those which do produce mental changes or mental effects, or, if there are corporeal feelings which produce corresponding mental states and mental action, there must be a something on which the effects can be wrought, and this something must be an independent organism. It is doubtless true that there are many corporeal feelings which are followed by no very important mental effects, especially during a sound state of bodily health. But it is equally true that, if there are corporeal feelings which influence our mental action, there must be an organism which is capable of being so influenced; and our experience and consciousness teach us that there is such a difference between corporeal feelings and mental phenomena that the probability of a difference in the originating causes becomes very great. We know that the mind can and does act with great force when bodily suffering is extreme; that it has an energy of its own which enables it to rise above all the power of physical pain to restrain or influence it. I must therefore follow out, as I had originally projected, my anatomical analysis of the mind as an independent spiritual organism.

In order to arrive at a correct conclusion concerning the structure of mind, we must first observe that there are four special corporeal organs by which the capability of the mind to receive impressions from matter is acted upon. It is through these means that the properties of matter, or those properties which can make themselves known to us, become known to us. The senses, as they are usually called, are sight, hearing, smell, and taste. The external organ of each of these senses is furnished with a set of nerves, the function of which is to transmit from that organ a wave of molecular motion along the fluid or semi-fluid substance inclosed in the nerve-tubes to the great nerve-center the brain, the central recipient of all such motions. Such, at least, is the theory, which may be accepted as a fact. But, then, the question remains, What is the intellectual perception or mental cognition of the idea suggested by one of these supposed transmissions of a wave of molecular motion? Is there a being, a person, a spiritual entity, conceiving the idea or having an intellectual perception of it? Or is there no such being, and while we attribute to the office of the nervous system the function of producing certain feelings or sensations in the brain, do these sensations or feelings constitute all that there is of consciousness?

It is impossible for me to conceive of consciousness as anything but an intuitive sense of his own existence, experienced by a being capable of such an experience, because endowed with such a faculty. It is certain that when we so regard consciousness we are not deceiving ourselves; for if any one will consider what would happen to him if he should lose this faculty of being sensible of his own existence, he will see that in the event of that loss he could neither distinguish himself from other persons, nor have any control over his own actions, or any cognition whatever. For this reason, the theory on which I made some criticisms in one of our late conversations is the one with which I contrast my conception of mind. If that theory fails to satisfy a reflecting person in regard to the nature of consciousness, as certified to him by his own experience, the hypothesis that the mind is an extended and organized being, of which a conception can be formed, and not an unextended and unorganized something of which no conception can be formed, must be accepted as the alternative.

I explained in our former discussion my understanding of Mr. Spencer's theory of the only ego that can be scientifically recognized; and, in order to encounter it by my own hypothesis, I will here restate its substantial position in a condensed form.