But the purpose of these Lectures requires something more, and that for two reasons. For, in the first place, the doctrine of necessity was most often in Bishop Butler's days derived from a conception of a Divine foreknowledge arranging everything by supreme Will, not from the conception of a blind mechanical rule holding all in its unrelaxing grasp. And though to the cold reason it may make no difference how the will is bound, yet to the moral sentiment the two kinds of compulsion differ as life and death. To have no liberty because of being absolutely in the hands of Almighty God is quite another thing from having no liberty, as being under the dominion of a dead iron rule. It seems possible to accept the one and call it an unfathomable mystery; but to accept the other is to call life a delusion and the moral law a dream. And in the second place, the doctrine of necessity advanced as a theory and based on arguments not resting on facts, is a very different antagonist from the same doctrine advanced as a conclusion of science, and as deducible from a mass of co-ordinated observations. We may dismiss the mere theory after showing that it has not substance enough to hold its ground in ordinary life. We cannot so treat what claims to be a scientific inference. The modern examination of the question begins with Hume, who maintains that the doctrine of liberty and that of necessity are both true and of course compatible with each other. But his arguments touch only the broad question whether they are true for practical purposes, not whether either is true in the strict sense and without exception or modification. To Kant's system, on the contrary, it was essential that both doctrines should be true in the strictest sense. Holding that invariable sequence was a law of Nature known independently of experience and applicable to all phenomena in the minutest detail, he could not allow that any act of the human will lay outside the range of this law. Such an act being a phenomenon must, in his view, be subject to the law which the constitution of our minds imposed on all phenomena apparent to us. And yet, on the other hand, holding that the eternal Moral Law made us responsible for all our acts, he could not but maintain that in the doing of those acts we must be free. His mode of reconciling the two opposites amounted to this, that our action throughout life considered as a whole is free, but that each separate act considered by itself is bound to the preceding acts by the law of invariable sequence. We may illustrate this by the familiar instance of a prism acting on a ray of light. The ray has or may have a colour of its own before it passes through the prism. The prism spreads it out and shows a series of colours. The order in which this series is arranged is determined by the character of the prism acting on the nature of the ray. The colours when combined give the colour of the ray; when