A feeble but zealous workman, I come to bring my stone; I come to do my work; I come to extract from the midst of the ruins what has not perished, what cannot perish. This course is at once a return to the past, an effort towards the future. I propose neither to attack nor to defend any of the three great schools that divide the eighteenth century. I will not attempt to perpetuate and envenom the warfare which divides them, complacently designating the differences which separate them, without taking an account of the community of method which unites them. I come, on the contrary, a devoted soldier of philosophy, a common friend of all the schools which it has produced, to offer to all the words of peace. The unity of modern philosophy, as we have said, resides in its method, that is to say, in the analysis of thought--a method superior to its own results, for it contains in itself the means of repairing the errors that escape it, of indefinitely adding new riches to riches already acquired. The physical sciences themselves have no other unity. The great physicians who have appeared within two centuries, although united amongst themselves by the same point of departure and by the same end, generally accepted, have nevertheless proceeded with independence and in ways often opposite. Time has re-collected in their different theories the part of truth that produced them and sustained them; it has neglected their errors from which they were unable to extricate themselves, and uniting all the discoveries worthy of the name, it has little by little formed of them a vast and harmonious whole. Modern philosophy has also been enriched during the two centuries with a multitude of exact observations, of solid and profound theories, for which it is indebted to the common method. What has hindered her from progressing at an equal pace with the physical sciences whose sister she is? She has been hindered by not understanding better her own interests, by not tolerating diversities that are inevitable, that are even useful, and by not profiting by the truths which all the particular doctrines contain, in order to deduce from them a general doctrine, which is successively and perpetually purified and aggrandized.