Logic of the Preface Paradox

The preface paradox is the apparent pragmatic inconsistency that occurs when the author of a book declares in its preface that despite believing that it is highly probable that everything the book maintains is true it is also highly probable that the book contains at least some errors. The preface paradox has often been presented as an example of a logically inconsistent belief that it is nevertheless rational to accept, supporting the suggestion that rationality has nothing immediately to do with avoiding formal logical inconsistency in one’s beliefs. In contrast with complicated received solutions, I explain a simple method of avoiding inconsistency in preface paradox assertions by indexing the two claims to distinct probability or justification sources, referencing in the first case the conscientious efforts to eliminate errors and in the second case the chagrin of past experience in discovering previously unsuspected errors in published writings. The solution thereby helps preserve the concept of rationality as logical consistency of belief, and avoids the conclusion that the preface paradox proves that it is sometimes rational to accept logically inconsistent beliefs. 1. The Preface Paradox The preface paradox is the apparent pragmatic inconsistency that occurs when an author declares in the preface of a book that, despite believing that everything the book asserts is true, it is also likely to contain at least some errors. The preface paradox is often presented as an example of a logically inconsistent belief that it is nevertheless rational to accept. The author offers the book for publication on the assumption that it is errorfree, while acknowledging perhaps from past experience or a general understanding of human fallibility that there is a high probability, despite good intentions and conscientious efforts to avoid mistakes, that a document as large and complicated as a book is likely to include at least some minor inaccuracies, which it is only prudent to admit. Thus, it appears rational to accept a logically inconsistent belief or several mutually logically inconsistent beliefs, that the same book is probably error-free and probably contains at least some errors. It is rational to believe that a carefully competently written book will harbor no mistakes at the Principia, 12(2) (2008), pp. 203–16. Published by NEL — Epistemology and Logic Research Group, Federal University of Santa Catarina (UFSC), Brazil.