Today I come to a new and final attempt at an introduction of the language-analytical conception of philosophy. It is orientated towards the idea of reason. The word ‘reason’ (Vernunft) is not used univocally. In the German Enlightenment vernünfteln was used to translate the Latin ratiocinari, just as today raisonner in French and to reason in English are still in use. The faculty of reason would accordingly consist in the capacity to argue. It is this that Kant has in mind when he defines reason in its logical sense as the faculty of making inferences (Critique of Pure Reason, B355). But from this there follows a second ‘transcendental’ definition, according to which reason is designated as ‘the faculty of principles’ (B356). ‘Principles’ are the first and, hence, unconditional propositions of a deductive system. From this there resulted for Kant a concept of reason according to which reason stands for the consciousness of unconditioned totality (B378 ff.). On this basis German Idealism then came to oppose reason, wholeness, dialectic, to the ‘mere’ understanding, and there began that disdain for the logical that is characteristic of the German development of the last century and a half. Despite this peculiar development of German philosophy the words Vernunft and vernünftig retained, in ordinary language, their original Enlightenment sense, whereas vernünfteln and räsonnieren are now only used in a pejorative sense. In ordinary language vernünftig means something like ‘well grounded’. And the demand to use one's reason means: one should not take over opinions unexamined, but enquire as to their grounds and counter-grounds. The capacity to argue is not only a capacity to make deductive inferences but, more generally, the capacity to justify statements. Ratio, raison, reason can mean both ‘ground’ (Grund) and ‘reason’ (Vernunft). The faculty of reason is the capacity of being able to answer for one's beliefs and actions (Latin: rationem reddere. Greek: logon didonai).

A conception of philosophy which is orientated towards the idea of reason thus takes up that aspect of the Aristotelian preliminary conception of philosophy which had been neglected in its ontological realization. There have been many attempts in the history of philosophy to develop a conception of philosophy as the science which radicalizes the aspect of justification which is present in all sciences; for example, in Plato, in Descartes, in German Idealism, in Husserl.