What is deductive inference? The question has been intensively addressed in discussions tracing back at least to Frege and to Lewis Carroll. A good answer needs to recognize two new elements: one from the domain of contents or propositions, and one from the realm of mental action. A good answer also has to explain the connection between these two elements. I argue that the new contents cannot be explained using extant materials from natural deduction or axiomatic systems; that the goal of logic should be characterized in terms of the new elements; and that properly deployed, these two new elements can be used to elucidate the role of knowing-that and knowing-how in deductive inference. The new elements also play a role in an account of justification more generally.
Christopher Peacocke is Johnsonian Professor of Philosophy at Columbia University. He taught at Oxford for many years, eventually as Waynflete Professor of Metaphysical Philosophy, before moving to New York in 2000. He has taught at Berkeley, UCLA, NYU, and University College London. He writes on the philosophy of mind, on the relations between metaphysics and epistemology, and is also currently writing on the perception of music.