H. P. Grice's Deductum

DEDUCTUM. deduction (Kant) Philosophical method, epistemology, metaphysics Deduction is normally used in a logical or geometrical sense for the derivation of a conclusion from premises, but Kant adopted a different use from the practice of jurists. The law distinguishes between the question of right (quid juris) and the question of fact (quid facti). Both these questions need to be proved. While questions of fact are proved through experience, the proof of questions of right is called deduction. In this sense, a deduction is a proof of the legitimacy of something. In his critical philosophy, Kant set out various a priori intuitions and concepts, but argued that he needed to provide justification and explanation of how they can be validly applied to objects. This procedure is what he called deduction. He further distinguished three types of deduction: metaphysical deduction, which is the argument that derives the categories from the twelve forms of judgment; empirical deduction, which shows the legitimacy of applying an empirical concept in terms of our experience of empirical objects; and transcendental deduction, which is carried out by a transcendental argument. The transcendental deduction is the central argument of the Critique of Pure Reason. “Now among the manifold concepts which form the highly complicated web of human knowledge, there are some which are marked out for pure a priori employment, in complete independence of all experience; and their right to be so employed always demands a deduction.” Kant, Critique of Pure Reason. deductive logic Logic Deductive logic analyzes the logical concepts related to deduction and classifies propositions in terms of their logical forms. It seeks to formulate logic explicitly by analyzing the logical forms of arguments and the relationship of valid entailment in deductive argument in order to reveal the forms of argument in which the conclusion is necessarily inferred from the premises. A proposition that implies a false conclusion cannot be true. An argument is valid if premises and the negation of the conclusion involve a self-contradiction. “The task of deductive logic is often defined as the explicit formulation of the implicitly recognised rules of deductive inference.” Pap, Elements of Analytic Philosophy. deductive-nomological model Philosophy of science A theory of explanation developed by Hempel. On this model, an event is explained by logically deducing the sentence describing it from a law-like generalization and a statement of certain initial conditions. The law-like generalizations are called nomological generalizations or covering laws. This model of explanation, abbreviated as the D-N model, can also apply to the covering laws themselves. A covering law can be explained by deducing it from a higher-order covering law or body of laws. The D-N model is a sub-model of the covering law model, with the inductive-statistical model considered to be another sub-model. Because it is the variant of greatest importance and most frequent employment, the deductive-nomological model is often taken as synonymous with the covering law model. “The general conception of explanation by deductive subsumption under general laws or theoretical principles . . . will be called the deductive nomological model, or the D-N model of explanation.” Hempel, Aspects of Scientific Explanation