Recently a number of philosophers (e.g. Feyerabend and Kuhn) have maintained that the meanings of terms in a scientific language are “theory-laden” or determined by the theory in which they occur, and thus that if the same term (e.g.; ‘mass’) occurs in different theories, it will take on different meanings in the different theories; so the theories are incommensurable. An often-stated corollary to this doctrine is the claim that possessors of different theories cannot express or possess the same facts since they attach different meanings to the terms used to give expression to the facts. Various attacks against this extreme doctrine on the relativity of facts have been mounted. Some of them consist in showing defective the argument advanced in support of this doctrine; but such criticisms at best show that the defenses offered for the doctrine are defective, not that the doctrine itself is defective.