indication of the fact that the basic question of logic has not yet reached the dimension of philosophical questioning.
Nowadays, however, that very discussion serves as a preparation for laying the foundations of logic. We find prolegomena to pure (philosophical) logic not in the realm of scholastic logic, but precisely in the one place where inquiry in logic is still alive in our day: in Edmund Husserl’s Logical Investigations, published in 1900–1901, which, although little enough understood, was the first book to shake up present-day logic again and to advance its productive possibilities.17 The first volume of these Logical Investigations is subtitled, “Prolegomena to Pure Logic,” which means it deals with what first has to be clarified prior to any and all logic.
The first volume is a principled refutation of psychologism as a form of skepticism and of relativism, followed by the positive presentation of the idea of pure logic. If the questions we posed [25] about skepticism and especially about its refutation are correct, then it follows that even contemporary philosophical logic has not gotten down to the real foundations. In fact its questions have not even moved in that direction. Instead, it is constructed on something it presumes to be self-evident: truth as the truth of propositions, truth as the validity of statements.18
Given what we said about transparency and about skepticism, it is clear that the question “What is truth?” will force us into some fundamental reflections.
However, because this course is also supposed to be of an introductory nature, it does not start right off with a treatment of the question “What is truth?” Instead, in part I of the course we want to get acquainted with the crucial historical origins of the problem of truth in the Western philosophy in which we ourselves stand. In so doing, we will rely on the authentic documents of the origin of philosophical logic, and we will glean, as it were, a collegium logicum from Aristotle
17. [Edmund Husserl, Logische Untersuchungen. Erster Theil: Prolegomena zur reinen Logik (Logical Investigations, Part One: Prolegomena to Pure Logic) and Zweiter Theil: Untersuchungen zur Phänomenologie und Theorie der Erkenntnis (Part Two: Investigations into the Phenomenology and Theory of Knowledge) (Halle: Max Niemeyer, 1900–1901). All citations from this work will follow the pagination of the first edition, which is the one Heidegger cites in this course. Texts of the first and second editions have been reissued as Husserliana (The Hague: Martinus Nijhoff), vol. XVIII, ed. Elmar Holenstein (1975), and vols. XIX/1 and XIX/2, ed. Ursula Panzer (1984). For an English edition see Logical Investigations, trans. J. N. Findlay, 2 vols. (London: Routledge & Kegan Paul / New York: Humanities Press, 1970).]
18. [This is only one of the many critiques of Husserl that Heidegger articulated during the Marburg years.]