It is to its origin that this work owes its fertilizing power, its classic strength, and the fact that it has given in so few pages the synthesis of so many series and groups of ideas.[3] It is the work of two Germans, but it is not either in its form or its basis the expression of personal opinion. It contains no trace of the imprecations, or the anxieties, or the bitterness familiar to all political refuges and to all those who have voluntarily abandoned their country to breathe elsewhere freer air. Neither do we find in it the direct reproduction of the conditions of their own country, then in a deplorable political state and which could not be compared to those of France and England socially and economically, except as regards certain portions of their territory. They brought to their work, on the contrary, the philosophic thought which alone had placed and maintained their country upon the level of contemporary history:--this philosophic thought which in their hands was undergoing that important transformation which permitted materialism, already renewed by Feuerbach combined with dialectics, to embrace and understand the movement of history in its most secret and until then unexplored causes,--unexplored because hidden and difficult to observe. Both were communists and revolutionists, but they were so neither by instinct, by impulse nor by passion. They had elaborated an entirely new criticism of economic science and they had understood the connection and the historic meaning of the proletarian movement on both sides of the Channel, in France and in England, before they were called to give in the Manifesto the programme and the doctrine of the Communist League. This had its center in London and numerous branches on the continent; it had behind it a life and development of its own.