But I have not done with this matter yet. We are here dealing with the central problem of things, and we must not leave it till we have made it as plain as possible. I will therefore re-state it in terms of another metaphor. Let us compare the universal matter, with its infinity of molecules, to a number of balls on a billiard-table, set in motion by the violent stroke of a cue. The balls at once begin to strike each other and rebound from the cushions at all angles and in all directions, and assume with regard to each other positions of every kind. At last six of them collide or cannon in a particular corner of the table, and thus group themselves so as to form a human brain; and their various changes thereafter, so long as the brain remains a brain, represent the various changes attendant on a man's conscious life. Now in this life let us take some moral crisis. Let us suppose the low desire to cling to some pleasing or comforting superstition is contending with the heroic desire to face the naked truth at all costs. The man in question is at first about to yield to the low desire. For a time there is a painful struggle in him. At last there is a sharp decisive pang; the heroic desire is the conqueror, the superstition is cast away, and '_though truth slay me_,' says the man, '_yet will I trust in it_.' Such is the aspect of the question when approached from one side. But what is it when approached from the other? The six billiard balls have simply changed their places. When they corresponded to low desire, they formed, let us say, an oval; when they corresponded to the heroic desire, they formed, let us say, a circle. Now what is the cause and what the conditions of this change? Clearly a certain impetus imparted to the balls, and certain fixed laws under which that impetus operates. The question is what laws and what impetus are these? Are they the same or not the same, now the balls correspond to consciousness, as they were before, when the balls did not correspond to it? One of two things must happen. Either the balls go on moving by exactly the same laws and forces they have always moved by, and are in the grasp of the same invincible necessity, or else there is some new and disturbing force in the midst of them, with which we have to reckon. But if consciousness is inseparable from matter, this cannot be. Do the billiard-balls when so grouped as to represent consciousness generate some second motive power distinct from, at variance with, and often stronger than, the original impetus? Clearly no scientific thinker can admit this. To do so would be to undermine the entire fabric of science, to contradict what is its first axiom and its last conclusion. If then the motion of our six billiard balls has anything, when it corresponds to consciousness, distinct in kind from what it always had, it can only derive this from one cause. That cause is a second cue, tampering with the balls and