In the first book of the _Novum Organon_ the great leader of the new philosophy undertook to set forth the dangers and difficulties which stand always in the way of clear and fruitful thought. Conscious that he was breaking entirely with the schools of the past, and ambitious of laying the firm foundations on which all future inquirers would have to build, it was natural that Bacon should pause on the threshold of his vast enterprise to take stock of the mental weaknesses which had rendered futile the labors of earlier thinkers, and which, if not carefully guarded against, would jeopardize the efforts of times to come. That the understanding may direct itself effectively to the search for truth it is necessary, he insisted, that it should have a full apprehension of the lapses to which it is ever liable, the obstacles with which it will constantly have to contend. A vague sense of peril is not enough. As a first condition of healthy intellectual activity we must learn to know our frailties for what they really are, estimate their consequences, and probe the secrets of their power. Bacon's statement of the sources of error and vain philosophizing is regarded by him as merely the _pars destruens_ or negative portion of his work--as it were, "the clearing of the threshing floor." But his aphorisms are packed close with solid and substantial thought, and well deserve the attention of all who would seriously devote themselves to the intellectual life. "True philosophy," as he conceived it, "is that which is the faithful echo of the voice of the world, which is written in some sort under the direction of things, which adds nothing of itself, which is only the rebound, the reflection of reality." To reach for ourselves, as nearly as we may, a philosophy which shall meet the terms of this exigent definition is, or should be, one chief purpose of our study and our thought. We may very well ask, then, what help so great and suggestive a thinker may give us on our way.