Together with concepts such as pillarization and consociational democracy, the notion of social transaction has been forged to account for national contexts where different subcultures coexist and yet simultaneously maintain their own autonomy. But while pillarization became a widely agreed-upon diagnosis of Belgian society, limited in its descriptive reach to this and a few similar contexts, social transaction, by contrast, has become part and object of a scientific practice stretching out from France as far as Canada. The paper seeks to better understand the notion’s emergence in Belgium and its relevance beyond this original context. We first examine what the concept reveals of its historical and intellectual context, and vice versa. Next, we show that its engagement with different and opposing sociological strands grants social transaction a typically ambivalent character that mirrors the experiences of its authors and their position within francophone sociology. The notion does not make unambiguous theoretical choices, but rather gives and takes between production (Touraine) and reproduction (Bourdieu), exchange (Mauss) and negotiation (Crozier). If despite its rootedness, the notion of social transaction has nevertheless gained relevance beyond Belgium, so we suggest, a plausible explanation might be found in its claim that the opacity of the social world stands as one of its most universal and productive traits.