To write the Biography of Philosophy while writing the Bio graphies of Philosophers is the aim of the following work. The expression Biography of Philosophy, though novel, may per haps be pardoned, because it characterizes a novel attempt. There have been numerous histories of philosophical schools some of these learned and laborious chronicles being little more than a collection of fragments and Opinions; others critical estimates of various systems; and others attempting to unite both of these plans. But the rise, growth, and development of Philosophy, as exhibited in these philosophical schools — in a word, the Life of Philosophy — has yet, I believe, had no bio grapher. My conception of such a task, and the principles which have guided the composition of the present attempt, are stated in the Introduction. It is usual, in presenting to the public a work destined for instruction, to show that such a work is wanted and, if other works on the subject already exist, to express a proper dis satisfaction at them, as an excuse for one's own audacity. So reasonable a practice invites imitation, even at the risk of appearing presumptuous.