Understanding Beliefs

Our beliefs constitute a large part of our knowledge of the world. We have beliefsabout objects, about culture, about the past, and about the future. We have beliefs about otherpeople, and we believe that they have beliefs as well. We use beliefs to predict, to explain, tocreate, to console, to entertain. Some of our beliefs we call theories, and we are extraordinarilycreative at constructing them. Theories of quantum mechanics, evolution, and relativity areexamples. But so are theories about astrology, alien abduction, guardian angels, and reincarnation.All are products (with varying degrees of credibility) of fertile minds trying to find explanationsfor observed phenomena. In this book, Nils Nilsson examines beliefs: what they do for us, how wecome to hold them, and how to evaluate them. We should evaluate our beliefs carefully, Nilssonpoints out, because they influence so many of our actions and decisions. Some of our beliefs aremore strongly held than others, but all should be considered tentative and changeable. Nilsson showsthat beliefs can be quantified by probability, and he describes networks of beliefs in which theprobabilities of some beliefs affect the probabilities of others. He argues that we can evaluate ourbeliefs by adapting some of the practices of the scientific method and by consulting expert opinion.And he warns us about "belief traps" -- holding onto beliefs that wouldn't survivecritical evaluation. The best way to escape belief traps, he writes, is to expose our beliefs to thereasoned criticism of others.

Nils J. Nilsson is Kumagai Professor of Engineering, Emeritus, in the Department of Computer Science at Stanford University. He is the author of The Quest for Artificial Intelligence: A History of Ideas and Achievements and other books. He lives in Oregon.