Large development of evaluation in social-intervention field is an answer to the state requisite for control and standardization. This demand, which is strongly influenced by a positivist point of view, finds its practical application in recommendations for fair professional manners. The way within those advises are written and set up reveals a more systemics logic of diffusion, than that which would have prevailed if there has simply been a causality relation. And the striking concepts to enlighten the point of this diffusion movement are that of the “complexity thought”. “L’Agence Nationale de l’Évaluation et de la qualité Sociale et Médico-sociale” plays the part of an intermediary to launch a learning process between the political decisioning and the achievement of evaluation in the units and departments.