=Summary.= On the whole, the inherited Puritanism of Locke was easily modified not only by his own moderate disposition, but also by his scientific interests and by his large political experiences. He naturally grew to be the apostle of the _via media_ between traditionalism and empiricism. He published practically nothing before he was sixty years old. After his return from exile his principal works appeared in swift succession. Two accidents formed turning-points in his life. His accidental meeting with Shaftesbury in 1666 turned him to politics; and secondly, at an informal meeting of friends in the winter of 1670–1671 the question about the nature of sensations was accidentally raised, out of which grew his great _Essay_. His life was primarily one of affairs and of large acquaintance with men and things. To him life was the first thing, his interest in politics came second, and his philosophy third. That his ideas should have been the basis of extreme philosophical and political beliefs on the Continent is natural enough when one remembers the perils of misinterpretation to the man who preaches the doctrine of the _via media_. =The Purpose of Locke.= In the historical perspective of two centuries we to-day see Locke in his _Essay on the Human Understanding_ delivering the inaugural address of the eighteenth century. He is making the first formal declaration of the intellectual rights of the individual in a lengthy, dry, and erudite psychological dissertation. Of course he never knew the historical importance of his own work. It grew out of the need of the hour. He would have been astonished to find himself the spokesman of the century of French Encyclopædists, materialists, and revolutionists, of English deists, of German Illuminati, of Hume, and of Voltaire. He had in mind to answer the restrictions of the high churchman on the one hand, and the arrogant claims of the atheists on the other, as to the power of the human intellect. He states that his design is to “inquire into the original certainty and extent of human knowledge.” In this declaration Locke foreshadows Kant, but he falls short of the insight of Kant. For Locke speaks for the spirit of the eighteenth and not the nineteenth century, and (1) he must keep within the range of concrete facts; (2) he must state only what can be stated clearly; and (3) he must be practical. It was, however, in its larger meaning a declaration of human freedom. Locke shows what limitations the human intellect has, what it can and what it cannot know. When the Enlightenment got momentum, it forgot the limitations to knowledge that the sober Locke had set down, and read in his words only a declaration of license. The _Essay_ differs from any previous modern philosophical writing. Man and not the universe is the subject. For the first time we find an examination of the laws of mind, and not of the laws of the universe.