Heidegger and Language

FIVE The Logic of Thinking

86 five The Logic of Thinking John Sallis From the beginning logic is conceived as the logic of thinking. Already in Greekthoughtlogicisassignedthetaskofidentifying,formulating,andformalizingthelawsofthinking .Thuslogicisobligedtoinvestigatethewaysin which concepts, judgments or propositions, and arguments in the shape of syllogisms are formed. What distinguishes logic from other cognitive disciplines , from other kinds of ἐπιστήμη or science, is that logic considers these various constructions only with respect to their form, that is, without any regard for their content. Thus, whether a syllogism is properly constructed so that the conclusion follows from the premises is purely a matter of the form of the constituent propositions and of the formal relation between them; the validity of the argument has nothing whatsoever to do with the content of the propositions, with what they are about. Because of this disregardorabstractionfromcontent ,formalizationisalreadyimplicitinthevery idea of logic. To this extent the modern mathematization of logic represents merely the fulfillment of a tendency that was in force from the beginning. This classical conception of logic is concisely expressed by Heidegger in his 1934 lecture-course on logic. Here he defines logic as “the science of the basic structures of thinking” and, more specifically, as “the science of the basic formal structures and rules of thinking.”1 Yet these definitions , given at the outset of the 1934 lecture-course, are stated, not by way of reaffirmation but rather as preparation for an Erschütterung of logic (as Heidegger calls it) that will have severe consequences for this discipline. This Erschütterung is one of several gestures that together may be called the deconstruction of logic. My primary concern in this essay is to discern precisely what is at stake in this deconstruction of logic—that is, what prompts it, how it is The logic of thinking · 87 carried out, and what remains to be considered in its wake. Yet this move occurs against the background of a concern with logic that goes back to the very beginning of phenomenology. Already in the Logical Investigations Husserl undertakes in a radicalizing way to retrieve and to ground logic. This venture is one that Husserl never abandons, and, in particular, it is powerfully renewed in Formal and Transcendental Logic. It is this same venture that is taken up and addressed by Heidegger in his early writings and lecture-courses, initially in its Husserlian form, then in a more independent and eventually deconstructive manner. (1) Logic is the science of the formal structures, rules, or laws of thinking. In this conception there is a basic ambiguity. This ambiguity readily gives rise to a misconception. Because of this misconception there arose a certain tendency in modern thought that puts in jeopardy the very status of logic as a pure science. It was in opposition to this tendency that Husserl undertook to retrieve the genuine sense of logic. The ambiguity lies in the conception of laws or rules of thinking; for they may be taken either as laws by which thinking occurs or as laws by which it ought to occur. They may be construed either as laws that govern actualprocessesofthinkinginthemannerthatnaturallawsgovernphysical processes; or they may be construed as laws that function as norms, laws that prescribe the course that thinking must follow in order to be formally in agreement with its object and hence possibly true or valid. The tendency that arises in modern thought emphasizes the first of these alternatives. Reinforced by empiricism, the tendency is to regard the laws of thinking as laws that actually govern the human psyche. For example , John Stuart Mill takes the law of non-contradiction to be based primarily on the fact that belief and disbelief are two mental states that excludeoneanother.Thus,heaccountsforthislawasarisingfromtheselfobservation in which we find that we cannot both believe something and not believe it; this self-observation is, then, according to Mill’s account, reinforced by our outward observation that when a certain phenomenon is present its opposite is always absent, as with light and darkness, sound and silence, equality and inequality. The law of non-contradiction he regards , then, as a generalization from all these facts. More generally, he 88 · john sallis regards all logical laws as merely generalizations based on factual experience , as general expressions of the actual workings of the human psyche. Thus, logic would need to be based on the scientific investigation of the human psyche, that is, on psychology. Such a consignment of logic to psychology is what is called psychologism. Husserl...