This article seeks rapprochement between the sociology of knowledge and philosophy of science by attempting to capture the best social constructionist insights within a strongly realistic philosophy of science. Key to doing so are separating the grounds for the individual scientist coming to know that P from those grounds for socially credentialing the claim that P within the relevant scientific subcommunity and showing how truth considerations can enter into the analysis of knowledge without interfering with social constructionist treatments of credentialing (...) claims. A detailed epistemology and associated account of the social credentialing of knowledge claims are presented. Close attention is paid to the epistemological and social aspects of the nature and role of observation reports, the interpretation of data, simplifications, idealizations, and approximations, and the nature of replication. The article contains a National Aeronautics and Space Administration remote-sensing case study and a detailed analysis of replication in the 1881–1933 Michelson-Morley-Miller interferometer ether studies. (shrink)