Doubt Truth to Be a Liar

by Graham Priest

Dialetheism is the view that some contradictions are true. This is a view which runs against orthodoxy in logic and metaphysics since Aristotle, and has implications for many of the core notions of philosophy. Doubt Truth to Be a Liar explores these implications for truth, rationality, negation, and the nature of logic, and develops further the defense of dialetheism first mounted in Priest's In Contradiction , a second edition of which is also available.

Genres: Philosophy, Logic, Nonfiction

240 pages, Hardcover

First published December 15, 2005

Reviews

[Riku Sayuj · Rating 4 out of 5]

Book 3: The Basic Instruments Of Philosophy

‘Doubt Truth to Be a Liar’, ostensibly the book being reviewed here, is a championing of the ideas of  dialetheism , which argues that some contradictions can indeed be true. Priest mounts an effective challenge against Aristotle’s fundamental Law of Non-Contradiction (as we will see, it is the heart of Book 3), and against the many philosophies and arguments that have grown up around Aristotle’s First Principle. This book is much more than a discussion on this particular book of the Metaphysics and touches on a variety of other Aristotelean works. But since I want to have something on each book of my Metaphysics reading up (so that I am forced to move to the next book only after I organize and summarize my notes of the former and because this book was a fascinating and well-argued counter to Aristotle’s flat-out assertion, and especially since the Symposium Aristotelicum is not available for this particular book) I have chosen this review as a place to primarily discuss Book 3 -- This is a disservice to Priest’s book which is wonderful reading if you want to explore further the role that contradiction plays in our thinking and logical maneuvering. Do check out other reviewers for more on the book.

To read about other Books of The Metaphysics, see here:  Book 1: A Preliminary Outline of Philosophy  & here: Book 2: An Introduction to Philosophical Problems.

I am using my parallel readings on Aristotle & Metaphysics to keep my notes/understanding of each book in separate pockets before bringing them together in a final review, if that is possible.

Book Gamma: Going Further

After the historical surveys and problems discussed in the first two books, Aristotle is now in a position to give his famous assertion on what is presumably his definitive statement of what philosophy and especially metaphysics is — It is the study of "being qua being". That is, while other sciences investigate limited aspects of being, metaphysics investigates being itself. This study of being qua being amounts to be the same thing as the study of the primary causes and principles, which has previously been said to be the task of philosophy, because the primary causes and principles are the causes and principles of being qua being.

This is because Being itself is primarily identified with the idea of substance, and also with unity, plurality (as we are later told, philosophy will interest itself in plurality, the contrary of unity, since all sciences study contraries, and so consider difference, dissimilarity, etc.), and a variety of other related concepts. Aristotle implies that he will be investigating these soon.

But before he sets out on the investigation, Aristotle needs to make his readers familiar with the basic tools of argumentation since proper, rigorous philosophy is also concerned with logic and the principles of demonstration, which are also very general, and hence concerned with being itself — In making this addition, he is resolving the dilemma posed by puzzle 2 of book Beta. Ideally, Aristotle seems to be saying, the reader should already be familiar with the Organon’s arguments before he/she goes further than this book. The bulk of the rest of book Gamma is, accordingly, devoted to the defense of the fundamental principles of demonstration/logic. Aristotle evidently feels that it will not be possible to be certain about the conclusions later to be drawn about substance, unless the principles of demonstration itself have first been vindicated.

The most fundamental principle according to Aristotle, the only thing he is prepared to elevate to the level of an axiom, is the principle of noncontradiction: nothing can both be something and not be that same something. To Aristotle, this is the First Principle of logical demonstration, which though not of course deducible, is the ultimate principle governing all being and all knowledge. Aristotle defends this principle exhaustively by arguing that it is impossible to contradict it coherently. Aristotle also presents in this connection the principle of non-contradiction is the Principle of the Excluded Middle, which states that there is no logical middle position possible between two contradictory positions. That is, a thing is either x or not-x, and there is no third possibility in-between those two positions.

Back on The Attack

Book Gamma concludes by looking back at Books 1 & 2 and uses the new principles the readers have now been made familiar with to launch another attack on, and reject, the several general claims of earlier philosophers: that everything is true, that everything is false, that everything is at rest, and that everything is in motion.

Aristotle proves that these claims amount to a rejection of the principle of non-contradiction. First, he deals with those who claim either that everything is true or that everything is false. Each of these claims is in fact self-destructive: if everything is true, then so is the denial that everything is true, and if everything is false, then so is the claim that everything is false. Secondly, he also refutes those who claim either that everything is at rest or that everything is in motion. That everything is not at rest is shown by the fact that the very proponent of the claim himself came into existence at some time in the past. That everything is not in motion is shown by the fact that for anything to be in motion there must be something which is not in motion and also by the fact that there are some things that are eternal.

The question of Motion, whether there is something permanently in motion and whether there is primary cause of motion which is itself permanently unmoving, is to be explored at greater length in book Lambda. In this book Aristotle expertly connects this fundamental exploration of metaphysics to the mistakes of his predecessors by subjecting them to the scrutiny of, according to him, the most basic techniques of demonstrative philosophy. After Book 2’s seemingly ‘unsolvable’ puzzles, if any reader felt that they might be in for a shaky and doubtful ride, this book shows that Aristotle is completely in control of the voyage and knows exactly where he is sailing. No worries.

[Harry Vincent · Rating 4 out of 5]

7.5/10

[Eric]

A supplemental textbook for my Symbolic Logic class at GWU, for when the author came to give a talk.

[Jonathan Carter · Rating 5 out of 5]

An interesting defence of dialetheism.