This chapter explores properties that bind individuals, knowledge, and communities, together. Section 1 introduces Hardwig’s argument from trust in others’ testimonies as entailing that trust is the glue that binds individuals into communities. Section 2 asks “what grounds trust?” by exploring assessment of collaborators’ explanatory responsiveness, formal indicators such as affiliation and credibility, appreciation of peers’ tacit knowledge, game-theoretical considerations, and the role moral character of peers, social biases, and social values play in grounding trust. Section 3 deals with establishing reliability standards for formation and breaching of trust. Different epistemic considerations and their underpinning of inductive risks are examined through various communication routes within a discipline, between disciplines, and to the public. Section 4 examines whether a collective entity can be trusted over and above trust that is given to its individual members. Section 5 deals with the roles technological artifacts play in distributed research and collective knowledge. It presents the common view in which genuine trust cannot, in principle, be accorded to artifacts, so as an opposite view. We show that what counts as a genuine object of trust is relevant to debates about the boundaries of collective agency and as a criterion for extended cognitive systems.