When a reader first comes from the vague, popular notions of Bacon's work to his definite proposals the effect is startling. Every one has heard that he contemplated a complete reform of the existing conceptions of human knowledge, and of the methods by which knowledge was to be sought; that rejecting them as vitiated, by the loose and untested way in which they had been formed, he called men from verbal generalisations and unproved assumptions to come down face to face with the realities of experience; that he substituted for formal reasoning, from baseless premises and unmeaning principles, a methodical system of cautious and sifting inference from wide observation and experiment; and that he thus opened the path which modern science thenceforth followed, with its amazing and unexhausted discoveries, and its vast and beneficent practical results. We credit all this to Bacon, and assuredly not without reason. All this is what was embraced in his vision of a changed world of thought and achievement. All this is what was meant by that _Regnum Hominis_, which, with a play on sacred words which his age did not shrink from, and which he especially pleased himself with, marked the coming of that hitherto unimagined empire of man over the powers and forces which encompassed him. But the detail of all this is multifarious and complicated, and is not always what we expect; and when we come to see how his work is estimated by those who, by greatest familiarity with scientific ideas and the history of scientific inquiries, are best fitted to judge of it, many a surprise awaits us.