Claudine Tiercelin (Collège de France) gives a talk for the Power Structuralism in Ancient Ontologies series. Abstract 'I will examine the conditions of possibility and the nature of metaphysical “knowledge”: 1) as compared with other types (mathematical, physical, ethical, philosophical knowledge; 2) from the point of view of its methods (conceptual analysis, thought experiments, empirical intuitions, a posteriori inferences, economy of research); 3) in relation to other traditional models of knowledge itself (justified true beliefs, reliabilism, or various virtue epistemology based strategies). Relying on the views I have defended in Le Doute en Question, Le Ciment des Choses or more recently, in La connaissance métaphysique, I will argue that metaphysical “knowledge” can indeed be achieved, provided 1) it relies on conceptual analysis and on the continuous massaging of our folk intuitions, 2) it trusts the a posteriori results of science without indulging into some kind of naturalized or scientistic metaphysics, and 3) it still aims, within the framework of a basically pragmatist and realistic strategy of knowledge viewed as inquiry, at the fixation of true beliefs and at the determination of the real nature of properties and things. In so doing, we should be able to avoid both excessive boldness and excessive humility.'