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 by them--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 upon it, were both matters on which he could throw no light. But elsewhere he has told us expressly that he does not mean this. This he expressly says is '_the interpretation of_ grosser _minds_,' and science will not for a moment permit us to retain it. The brain contains no '_entity usually occupied we know not how amongst its molecules_,' but at the same time separable from them. According to him, this is a '_heathen_' notion, and, until we abandon it, '_no approach_,' he says, '_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 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 perfectly 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_,' and which, as Dr. Tyndall has said elsewhere, science forbids us to believe in? Surely for an exact thinker this is thought in strange confusion. '_Matter_,' he says, '_I define as that mysterious something by which all this is accomplished_;' and yet here we find him, in the face of this, invoking some second mystery as well. And for what reason? This is the strangest thing of all. He believes in his second Incomprehensible _because_ he believes in his first Incomprehensible. '_If I reject one result_,' 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 existence of a personal God, and a variety of other '_heathen_' doctrines also. But, applied in this way, it is evident that the argument fails to move him; for a belief in a personal God is one of the first things that his science rejects.