"Were it fit to trouble thee," says Locke in his Epistle to the Reader, "with the history of this _Essay_, I should tell thee that five or six friends meeting at my chamber, and discoursing on a subject very remote from this, found themselves quickly at a stand by the difficulties that rose on every side. After we had a while puzzled ourselves, without coming any nearer a resolution of those doubts which perplexed us, it came into my thoughts that we took a wrong course; and that, before we set ourselves upon inquiries of that nature, it was necessary to examine our own abilities, and see what objects our understandings were or were not fitted to deal with. This I proposed to the company, who all readily assented; and thereupon it was agreed that this should be our first inquiry." This passage may serve not only to describe the occasion of Locke's _Essay_, but also to indicate the circumstance which constitutes the peculiar merit and originality of Locke as a philosopher. The science which we now call Psychology, or the study of mind, had hitherto, amongst modern writers, been almost exclusively subordinated to the interests of other branches of speculation. Some exception must, indeed, be made in favour of Hobbes and Gassendi, Descartes and Spinoza; but all these authors treated the questions of psychology somewhat cursorily, while the two former seem usually to have had in view the illustration of some favourite position in physics or ethics, the two latter the ultimate establishment of some proposition relating to the nature or attributes of God. We may say then, without much exaggeration, that Locke was the first of modern writers to attempt at once an independent and a complete treatment of the phenomena of the human mind, of their mutual relations, of their causes and limits. His object was, as he himself phrases it, "to inquire into the original, certainty, and extent of human knowledge; together with the grounds and degrees of belief, opinion, and assent." This task he undertakes not in the dogmatic spirit of his predecessors, but in the critical spirit which he may be said to have almost inaugurated. As far as it is possible for a writer to divest himself of prejudice, and to set to his work with a candid and open mind, seeking help and information from all quarters, Locke does so. And the effect of his candour on his first readers must have been enhanced by the fact, not always favourable to his precision, that, as far as he can, he throws aside the technical terminology of the schools, and employs the language current in the better kinds of ordinary literature and the well-bred society of his time. The absence of pedantry and of _parti pris_ in a philosophical work was at that time so rare a recommendation that, no doubt, these characteristics contributed largely to the rapid circulation and the general acceptance of the _Essay_.