The Principle of Reason, the text of an important and influential lecture course that Martin Heidegger gave in 1955–56, takes as its focal point Leibniz's principle: nothing is without reason. Heidegger shows here that the principle of reason is in fact a principle of being. Much of his discussion is aimed at bringing his readers to the "leap of thinking," which enables them to grasp the principle of reason as a principle of being. This text presents Heidegger's most extensive reflection on the notion of history and its essence, the Geschick of being, which is considered on of the most important developments in Heidegger's later thought. One of Heidegger's most artfully composed texts, it also contains important discussions of language, translation, reason, objectivity, and technology as well as remarkable readings of Leibniz, Kant, Aristotle, and Goethe, among others.

The text of a lecture course that Heidegger gave in 1955-56, takes as its focal point Leibniz's principle: nothing is without reason.

The Principle of Sufficient Reason (PSR) says that all contingent facts must have explanation. In this 2006 volume, which was the first on the topic in the English language in nearly half a century, Alexander Pruss examines the substantive philosophical issues raised by the Principle Reason. Discussing various forms of the PSR and selected historical episodes, from Parmenides, Leibnez, and Hume, Pruss defends the claim that every true contingent proposition must have an explanation against major objections, including Hume's imaginability argument and Peter van Inwagen's argument that the PSR entails modal fatalism. Pruss also provides a number of positive arguments for the PSR, based on considerations as different as the metaphysics of existence, counterfactuals and modality, negative explanations, and the everyday applicability of the PSR. Moreover, Pruss shows how the PSR would advance the discussion in a number of disparate fields, including meta-ethics and the philosophy of mathematics.

The nature of human reason is one of the thorniest of mysteries in philosophy. The reason appears in many specific forms within general areas such as cognition, thinking, experiencing beauty, and moral judgment. These forms are “perfectly” known in philosophy, yet an unknown pattern has been noticed which shows us that they are all a variation of the same theme: truth is an identity relation between the “thought” and “reality”; justice is an identity relation between the given and the deserved; beauty is an identity relation as rhyme is an identity relation between the final sounds of words; rhythm is an identity relation between time intervals; symmetry is an identity relation between two halves; proportion is an identity relation between two ratios; anaphora is an identity relation between the initial words. Particular things are identities in themselves and universals are identities between particulars. One idea associates another idea identical to it; an analogy is an identity between relations; induction is an identification between the known and unknown instances; and all the logic rests on the law of identity. What is common for all of them is the nature of reason itself.

Kant once famously declared in the Prolegomena that "it was the objection of David Hume that first, many years ago, interrupted my dogmatic slumber." Abraham Anderson here offers an interpretation of this utterance, arguing that Hume roused Kant not (as has often been thought) by challenging the principle that "every event has a cause" which governs experience, but rather by attacking the principle of sufficient reason, the basis of both rationalist metaphysics and the cosmological proof of the existence of God. This suggestion, Anderson proposes, allows us to reconcile Kant's declaration with his later assertion that it was the Antinomy of pure reason - the clash of opposing theses - that first woke him from dogmatic slumber. For the Antinomy suspends the dogmatic principle of sufficient reason; in doing so, Anderson proposes, it is extending Hume's attack on that principle. This reading of Kant also explains why Kant speaks of "the objection of David Hume" after mentioning Hume's attack on metaphysics. The "objection" that Kant has in mind, Anderson argues, is a challenge to metaphysics, rather than to the foundations of empirical knowledge. Consequently, Anderson's analysis issues a new view of Hume himself-as primarily interested, not in the foundations of experience, but in the problem of metaphysics and theology. It thereby positions Kant and Hume as champions of the Enlightenment in its struggle with superstition. Shedding new light on the connection between two of the most influential figures in the history of philosophy, this volume will appeal not only to scholars of Kant, Hume, and early modern philosophy, but to philosophers and students interested in the history of philosophy and metaphysics generally.

"Most modern philosophers attempt to solve the problem of morality from within the epistemological assumptions that define the dominant cultural perspective of our age. Alan Gewirth's Reason and Morality is a major work in this ongoing enterprise. Gewirth develops, with patience and skill, what he calls a 'modified naturalism' in which morality is derived by logic alone from the concept of action. . . . I think that the publication of Reason and Morality is a major event in the history of moral philosophy. It develops with great power a new and exciting position in ethical naturalism. No one, regardless of philosophical stance, can read this work without an enlargement of mind. It illuminates morality and agency for all."—E. M. Adams, The Review of Metaphysics "This is a fascinating study of an apparently intractable problem. Gewirth has provided plenty of material for further discussion, and his theory deserves serious consideration. He is always aware of possible rejoinders and argues in a rigorous manner, showing a firm grasp of the current state of moral and political philosophy."—Mind