Putting Logic in Its Place: Formal Constraints on Rational Belief

Putting Logic in Its Place: Formal Constraints on Rational Belief

Putting Logic in Its Place: Formal Constraints on Rational Belief

Putting Logic in Its Place: Formal Constraints on Rational Belief

Synopsis

What role, if any, does formal logic play in characterizing epistemically rational belief? Traditionally, belief is seen in a binary way - either one believes a proposition, or one doesn't. Given this picture, it is attractive to impose certain deductive constraints on rational belief: that one's beliefs be logically consistent, and that one believe the logical consequences of one's beliefs. A less popular picture sees belief as a graded phenomenon. This picture (explored more by decision-theorists and philosophers of science thatn by mainstream epistemologists) invites the use of probabilistic coherence to constrain rational belief. But this latter project has often involved defining graded beliefs in terms of preferences, which may seem to change the subject away from epistemic rationality. Putting Logic in its Place explores the relations between these two ways of seeing beliefs. It argues that the binary conception, although it fits nicely with much of our commonsense thought and talk about belief, cannot in the end support the traditional deductive constraints on rational belief. Binary beliefs that obeyed these constraints could not answer to anything like our intuitive notion of epistemic rationality, and would end up having to be divorced from central aspects of our cognitive, practical, and emotional lives. But this does not mean that logic plays no role in rationality. Probabilistic coherence should be viewed as using standard logic to constrain rational graded belief. This probabilistic constraint helps explain the appeal of the traditional deductive constraints, and even underlies the force of rationally persuasive deductive arguments. Graded belief cannot be defined in terms of preferences. But probabilistic coherence may be defended without positing definitional connections between beliefs and preferences. Like the traditional deductive constraints, coherence is a logical ideal that humans cannot fully attain. Nevertheless, it furnishes a compelling way of understanding a key dimension of epistemic rationality.

Excerpt

When people talk informally about belief, “rational” and “logical” are often used almost synonymously. And even those who think carefully and precisely about rational belief often take logic to play an important role in determining which beliefs are rational. Explaining the importance of logic to students, philosophers often say things like, “Rational beliefs must be logically consistent with one another, ” or “If you believe the premises of a valid argument, then, if you are rational, you must believe the conclusion.” This book aims to show that logic does indeed play an important role in characterizing ideally rational belief, but that its role is quite different from what it is often assumed to be.

The first chapter sets up parameters for the book's approach: it will focus on epistemic (rather than pragmatic) rationality; it will look at conditions on simultaneous rational beliefs (rather than on rational changes of belief); and it will concentrate on global rationality conditions for an agent's whole system of beliefs (rather than on local conditions for the rationality of particular beliefs). These choices are designed to focus the inquiry where formal logic is most likely to be useful in characterizing ideal rationality.

The second chapter ties the book's central question to a choice between two basic conceptions of belief. The standard binary model sees belief as an all-or-nothing state: either you believe P, or you don't. The graded model sees belief as coming in degrees. The two conceptions invite very different formal rationality conditions. Rational binary beliefs are often held to be subject to deductive cogency , which requires that an agent's beliefs form a logically consistent set which includes all the logical consequences of what the agent believes. Graded beliefs are often held to be subject to

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.