This lecture intends to show how thought about ambiances allows to make more complex the sociology of action and to identify some political stakes in urban developments. The sociology of action's credit is to link the issue of space with the practice one. Nevertheless this ecological prospect first of all point out the cognitive aspect of perception although the ambiance's problematic underlines her emotional and temporal size. We put to the test the hypothesis according to the fact that public space can encourage or restrain urban behavior in axiologic meaning of this term, refering to Simmel's analyse and Foucault and Sennett as well.