It is an honor to take part in this Festschrift for Joseph M. Perillo, scholar of contract law and friend and mentor to so many contracts teachers and practitioners. As the General Editor of the Revised Edition of Corbin On Contracts, Professor Perillo is advancing contracts scholarship on the widest scale. He has, of course, also made many important contributions to specific areas of the subject. In particular, with his longtime collaborator, the late John D. Calamari, Professor Perillo contributed a famous article, A Plea For a Uniform Parol Evidence Rule and Principles of Contract Interpretation, 42 Ind. L.J. 333 (1967), to the literature of contract interpretation. I have been revising Corbin's discussion of the parol evidence rule, so I have the benefit of Joe both as editor and as fellow scholar. I hope that this essay does him justice.