Abstract
Exploring the social characteristics of scientific knowledge and rationality has been an intrinsic problematic of science and technology studies (STS). After examining sociological studies of scientific communities and social studies of scientific knowledge, STS enquiries now have turned to the role of knowledge and knowing in the constitution of the known object. Among them, Actor-Network Theory (ANT) is an important approach.This paper first delineates this ontological turn of ANT: ontology-in-practice. Ontology-in-practice specifies the relationally emergent, mediated, and heterogeneous constitution of being-in-action, which is not a transcendental schema of beings and essences in the universe once and for all. It is argued that most criticisms against ANT and its political implications are due to critics' failure to understand this radical ontology. To remedy this, the paper turns to the historical ontology as effective history proposed by Foucault, which is similar to ontology-in-practice, so as to illuminate how ANT could be a critical perspective both in its scholarship and practice.