by most of the philosophical writers of the eighteenth century. However divergent in other respects, Hume and Berkeley, Hartley and Reid, the French Sensationalists, Kant, all commence their investigations by inquiring into the constitution, the capacities, and the limits of the Human Mind. Nor can any system of speculation be constructed on a sound basis which has neglected to dig about the foundations of human knowledge, to ascertain what our thoughts can and what they cannot compass, and what are the varying degrees of assurance with which the various classes of propositions may be accepted by us. Two cautions, indeed, are necessary in applying this procedure. We must never forget that the mind is constantly in contact with external nature, and that therefore a constant action and reaction is taking place between them; and we must never omit to base our inductions on an examination of other minds as well as our own, bringing into the account, as far as possible, every type and grade of mental development. It was not, however, only its general spirit and direction which Locke impressed on the philosophy of the eighteenth century. He may almost be said to have recreated that philosophy. There is hardly a single French or English writer (and we may add Kant) down to the time of Dugald Stewart, or even of Cousin, Hamilton, and J. S. Mill, who does not profess either to develope Locke's system, or to supplement, or to criticise it. Followers, antagonists, and critics alike seem to assume on the part of the reader a knowledge of the _Essay on the Human Understanding_, and to make that the starting-point of their own speculations. The office which Bacon assigns to himself with reference to knowledge generally might well have been claimed by Locke with reference to the science of mind. Both of them did far more than merely play the part of a herald, but of both alike it was emphatically true that they "rang the bell to call the other wits together." CHAPTER IX. LOCKE'S OPINIONS ON RELIGION AND MORALS, AND HIS THEOLOGICAL WRITINGS.