In an attempt to refine the concept of uncertainty, this paper elaborates an ontology of the social world concentrating on individuals, institutions and technology. It shows the strong entwinement of the ontological aspects of the conceptualisation of uncertainty and epistemological ones. It highlights the ontological and epistemological dimensions of different concepts of uncertainty, such as fundamental uncertainty, procedural uncertainty, ambiguity and weak uncertainty (or risk). It also comments on a few writings that distinguish varieties of uncertainty with adjectives such as 'ontological' and 'epistemological' or 'epistemic'.283365378