tion of science may be expressed thus. It may be compared to an engineer, with no knowledge of acoustics, who exhibits a steam-engine to us and sets it working. He can explain to us every source and every secret of its movements; but he cannot explain to us why, as it moves, it hums.

And next, how does the tune emerge? Let us here drop the metaphor of the steam-engine, as, if that were pressed too far, it might seem that the answer to this second question was begged by it. Let us again compare the brain to an instrument, out of which some tune sounds to us and then the second question will amount to this:-Is the brain a piano, or a musical box? Or again, we may express both questions in terms of the same metaphor; and the first question will be, why, when struck, are the piano-strings resonant? And the second will be, how is the mechanism moved that strikes them-by a musician, or by a revolving barrel ?

Here, then, are the two questions, and we may say with sufficient accuracy, the only two, that, according to Dr. Tyndall, science has left unsolved; and in this view he is certainly right, to a very great degree, and for the present we may take for granted that he is wholly right. One point, however, seems altogether to escape him; and that is what I shall now proceed to.

It is true, as we have seen, that he separates the two questions we are dealing with, but, at the same time, he confuses them. He failed to see that not only are they two questions, but that they belong to two different worlds, and that certainty or doubt about either of them means two very different things.

As to the first question, why is it that the brain is the organ of consciousness?-here is a point on which, so far as our practical views go, we can rest content in ignorance. And if any theologian hacks and scourges' Dr. Tyndall for his views thus far, he must, beyond all doubt, be a very foolish theologian indeed. The whole bearing of this matter Dr. Tyndall seems to strangely magnify, and he fancies himself assaulted by opponents who in reality have no existence. Let a man be never so theological, and never so pledged to a faith in myths and mysteries, he would not have the least interest in denying that the brain, though we know not how, is, for us, the only organ of thought, of mind, or of spirit. Let him have never so firm a faith in an immortal life, yet he knows that this immortal has certainly put on mortality, through an inexplicable contact with matter; and his faith is not in the least shaken by learning that this point of contact is the brain. He may admit with the utmost readiness that the brain is the only instrument through which the spiritual life is made at the same time human life; and that the moral state of a saint might conceivably be detected by a spectroscope. At first sight, doubtless, this may appear somewhat startling; but there is nothing really in it that is either strange or formidable. Dr. Tyndall says that the

view indicated can, he thinks,' be maintained against all attack.' But why he should apprehend an attack at all, and why he should only think that it would be unsuccessful, it is somewhat hard to conceive. To say that a spectroscope as applied to the brain might conceivably detect such a thing as sanctity, is little more than to say that our eyes so applied to a face can actually detect such a thing as anger. There is nothing in that doctrine to alarm the most mystical of believers. In the completeness with which it is now brought before us, it is doubtless new, and will doubtless tend presently to clarify human thought. But no one need fear to accept it as a truth; and probably before long we shall all accept it as a truism. It is not denying the existence of a soul, to say that it cannot stir in matter, without leaving some impress on matter, any more than it is denying the existence of a pianist, to say that he cannot play to us without striking the notes of his piano. Dr. Tyndall then need hardly have used so much emphasis and iteration in affirming that every thought and every feeling has its definite mechanical correlative, and is accompanied by a certain breaking up and remarshalling the atoms of the brain.' And he is no more likely to be 'hacked and scourged' for doing so than he would be for affirming that every note we hear in a piece of music has its definite physical correlative in the mechanics of the piano-that it is accompanied by a depression and a rising again of some particular key. In his views thus far the whole world may agree with him; and when he says this, and when he informs us that in these views there is still involved a mystery, it may rather be said that he agrees with the world, than that the world agrees with him. The passage to mind from matter is, Dr. Tyndall says, unthinkable. The common sense of mankind has always said the same. We have here something, not which we are doubtful how to explain, but which we cannot explain at all. We have not to choose or halt between alternative conjectures; for there are absolutely no conjectures to halt between. We are now, as to this point, in the same state in which we always have been. We are in theoretical ignorance, but in no practical perplexity.

But now let us pass on to the second question, and it will appear that the whole case is different. We will first see how this question is put and treated by Dr. Tyndall; and we will then examine what his treatment comes to. Is it true, he asks, that, as many physicists hold it is, the physical processes are complete in themselves, and would go on just as they do, if consciousness were not at all implicated,' as an engine would go on working, even though it did not hum, or as a musical box would go on playing even though there were no ear to listen to it? Or, do states of consciousness enter as links into the chain of antecedence and sequence, which gives rise to bodily actions?' And here comes Dr. Tyndall's answer. 'Speaking for myself,' he says, 'I have no power of imagining such states inter

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posed between the molecules of the brain, and influencing the transference of motion among the molecules. The thing eludes all mental presentation. But,' he adds, 'the production of consciousness by molecular motion is to me quite as unpresentable to the mental vision, as the production of molecular motion by consciousness. If I reject one result I reject both. I, however,' and here Dr. Tyndall rises to his highest pitch of sublimity, with all the adjuncts of capitals and italics,- I, however, reject neither, and thus stand in the presence of two Incomprehensibles, instead of one Incomprehensible.'

Now what does all this mean? There is one meaning of which the words are capable, which would make them perfectly clear and coherent; but that meaning, as we shall see presently, cannot possibly be Dr. Tyndall's. They would be perfectly clear and coherent if he meant this-that the brain was a natural instrument, in the hands of a supernatural player; but that why the instrument should be able to be played upon, and how the player should be able to play on it, were both matters on which he could throw no light. But elsewhere he tells us expressly that he does not mean this. This, he expressly says, 'is the interpretation of grosser minds,' which science will not for a moment permit us to retain. The brain contains no 'entity,' 'usually occupied, we know not how, among its molecules,' but separable from them. This, he tells us, is a heathen' notion, and until we abandon it, no approach to the subject is possible.' What does he mean then, when he tells us he rejects neither result,' when he tells us that he believes that molecular motion produces consciousness, and also that consciousness in its turn again produces molecular motion? when he tells us distinctly of these two, that 'observation proves them to interact'? If such language as this means anything, it must have reference to two distinct forces, one material and the other immaterial. Indeed, does he not himself say so? Does he not tell us that one of the beliefs he does not reject is the belief in states of consciousness interposed between the molecules of the brain, and influencing the transference of motion among the molecules'? It is clear, then, that these states are not molecules -in other words, they are not material. But if not material, what are they, acting on matter, and yet distinct from matter? What can they belong to, but that heathen' thing the soul-that entity, which could be thrown out of the window,' which Dr. Tyndall says elsewhere, science forbids us to believe in? Surely, for an exact thinker, this is thought in a strange confusion. He has spiritualised materialism by an enlarged definition of matter; he has defined it as 'that mysterious something' by which all that is is accomplished, and yet here we find him, in the face of this, declaring his belief in some second mystery as well. And for what reason? This is the strangest thing of all. He believes in the second Incomprehensible, because he believes in the first Incomprehensible. If I reject one,'

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he says, I must reject both. I, however, reject neither.' But why? Because one undoubted fact is a mystery, is every mystery an undoubted fact? Such is Dr. Tyndall's logic in this remarkable utterance; and if this logic be valid, we can at once prove to him the truth of the Christian Trinity, and a variety of other heathen' doctrines also. But it is evident that, if applied in this way, such an argument would fail to move him. No one could be so quick as he to detect the futility of it. What shall we say of him then, when he applies it in his own way? We can say simply this-that his mind, for the time being, is in a state of such confusion that he is incapable really of clearly meaning anything. What his position logically must be, what in other moments he avows it to be, is plain enough. It is essentially that of a man confronted by one Incomprehensible only, not confronted by two. But, looked at in certain ways, or rather looked from in certain ways, this position seems to stagger him. The problem of existence reels and grows dim before him; and he fancies he detects the presence of his two Incomprehensibles, when he has really only seen one Incomprehensible double. If this be not his case, it must be one that, intellectually, is even weaker than this. It must be that, not of a man with a single coherent theory, which his intellect in its less vigorous moments sometimes relaxes its hold upon; but it must be that of a man with two hostile theories, which he vainly imagines to be one, and which he inculcates alternately, each with an equal emphasis.

This bewilderment I impute to Dr. Tyndall is so important and so characteristic of the whole school he belongs to, that I must pause a moment longer to illustrate its reality, no matter to what cause we attribute it—to his vacillation between two theories, or his intermittent grasp of one.

Although he has proclaimed so loudly that the emergence of consciousness from matter must for ever remain a mystery, he yet shows indications of a hope that it may still be solved. He thus quotes with approval, and with an implication that he leans himself to the view expressed in them, the following words of Ueberweg, whom he calls one of the subtlest heads that Germany has produced.'

What happens in the brain (says Ueberweg) would, in my opinion, not be possible, if the process which here appears in its greatest concentration did not obtain generally, only in a vastly diminished degree. Take a pair of mice and a cask of flour. By copious nourishment the animals increase and multiply, and in the same proportion sensations and feelings augment. The quantity of these latter possessed by the first pair is not simply diffused among their descendants, for in that case the last would feel more feebly than the first. The sensations and the feelings must necessarily be referred back to the flour, where they exist, weak and pale it is true, and not concentrated, as in the brain.

'We may not,' Dr. Tyndall adds by way of a gloss to this, 'be

able to taste or smell. alcohol in a tub of fermented cherries, but by distillation we obtain from them concentrated Kirschwasser. Hence Ueberweg's comparison of the brain to a still, which concentrates the sensation and feeling pre-existing, but diluted, in the food.'

Let us now compare this with the following. It is no explanation,' says Dr. Tyndall, to say that objective and subjective are two sides of one and the same phenomenon. Why should phenomena have two sides? There are plenty of molecular motions which do not exhibit this two-sidedness. Does water think or feel when it runs into frost ferns upon a window pane? If not, why should the molecular motions of the brain be yoked to this mysterious companion consciousness?'

Here we have two views, diametrically opposed to each other, the one suggested with approval, and the other implied as his own, by the same writer, and in the same short essay. The first view is that consciousness is the general property of all matter, just as motion is. The second view is that consciousness is not the general property of matter, but the inexplicable property of the brain only.

Here again we have a similar inconsistency. Upon one page Dr. Tyndall says that when we have exhausted physics, and reached its very rim, a mighty Mystery still looms beyond us. We have made no step towards its solution. And thus it will ever loom.' And on the opposite page he says this: If asked whether science has solved, or is likely in our day to solve, the problem of the universe, I must shake my head in doubt.'

Further, I will remind the reader of Dr. Tyndall's arguments, some time since, against any outside designer or creator of the material universe. He argued that such did not exist, because his supposed action was not definitely presentable. He challenged the theist (the theist addressed at the time was Dr. Martineau) to give him some account of his God's workings; and When he does this,' said Dr. Tyndall, I shall "demand of him an immediate exercise " of the power" of definite mental presentation." If he fails here, his case is at once disproved; for nothing exists that is not thus presentable.' Let us compare this with his dealing with the fact of consciousness. Consciousness, he admits, is not thus presentable; and yet consciousness, he admits, exists.

Instances might be multiplied of the same vacillation and confusion of thought the same inability to be constant to one train of reasoning. But those just given suffice. What weight can we attach to a man's philosophy, who after telling us that consciousness may possibly be an inherent property of matter, of which the receipt of reason is a limbeck only,' adds, in the same breath almost, that matter generally is certainly not conscious, and that consciousness comes to the brain we know not whence nor wherefore? What shall we say of a man who in one sentence tells us that it is impossible