Abstract

Although the truth value (falsity) of "Henry knows that (dogs live in trees and beavers chew wood)" remains unchanged no matter what sentence is substituted in it for "beavers chew wood", we want not to regard the second as a truth functional component (tfc) of the first. Many definitions of "tfc" (e.g., Quine's) fail to insure satisfaction of the following principle: if p is a component of r which is in turn a component of q, then p is a tfc of q if and only if 1) p is also a tfc of r, and 2) r is also a tfc of q.