With one exception, all of the papers in this volume were originally presented at a conference held in April, 1978, at The Ohio State University. The excep tion is the paper by Wilfrid Sellars, which is a revised version of a paper he originally published in the Journal of Philosophy, 1973. However, the present version of Sellars' paper is so thoroughly changed from its original, that it is now virtually a new paper. None of the other nine papers has been published previously. The bibliography, prepared by Nancy Kelsik, is very extensive and it is tempting to think that it is complete. But I believe that virtual com pleteness is more likely to prove correct. The conference was made possible by grants from the College of Human ities and the Graduate School, Ohio State University, as well as by a grant from the Philosophy Department. On behalf of the contributors, I want to thank these institutions for their support. I also want to thank Marshall Swain and Robert Turnbu~l for early help and encouragement; Bette Hellinger for assistance in setting up the confer ence; and Mary Raines and Virginia Foster for considerable aid in the pre paration of papers and many other conference matters. The friendly advice of the late James Cornman was also importantly helpful. April,1979 GEORGE S. PAPPAS ix INTRODUCTION The papers in this volume deal in different ways with the related issues of epistemic justification or warrant, and the analysis of factual knowledge.