Academic freedom and tenure, both cherished institutions of higher education, are currently under attack by many both outside and within the academy. Richard DeGeorge argues that they can be defended on ethical grounds only if they are joined with appropriate accountability, publicly articulated and defended standards, and conscientious enforcement of these standards by academic institutions and the members of the academic community.

Richard Rorty is famous, maybe even infamous, for his philosophical nonchalance. His groundbreaking work not only rejects all theories of truth but also dismisses modern epistemology and its preoccupation with knowledge and representation. At the same time, the celebrated pragmatist believed there could be no universally valid answers to moral questions, which led him to a complex view of religion rarely expressed in his writings. In this posthumous publication, Rorty, a strict secularist, finds in the pragmatic thought (...) of John Dewey, John Stuart Mill, William James, and George Santayana, among others, a political imagination shared by religious traditions. His intent is not to promote belief over nonbelief or to blur the distinction between religious and public domains. Rorty seeks only to locate patterns of similarity and difference so an ethics of decency and a politics of solidarity can rise. He particularly responds to Pope Benedict XVI and his campaign against the relativist vision. Whether holding theologians, metaphysicians, or political ideologues to account, Rorty remains steadfast in his opposition to absolute uniformity and its exploitation of political strength. (shrink)

This topically organized, interdisciplinary anthology provides competing perspective on the claim that western culture faces a moral crisis. Using clearly written, accessible essays by well-known authors in philosophy, the social sciences, and the humanities, the book introduces students to a variety of perspectives on the current cultural debate about values that percolates beneath the surface of most of our social and political controversies.

Richard Rorty does have something ‘to say to [Black Americans]’ and to their racially conscious nonblack allies in the sense that his understanding of liberalism, his prophecies about the future and his urgent appeals to the American Left all paint a picture of a white middle class fully prepared to make life increasingly miserable for Black Americans unless it is ‘protected from catastrophe’. Rorty hopes that this group will undergo a moral transformation that enables it to see (...) past its narrow group interests, but doubts that it will. He, nevertheless, prescribes a politics of hope and appeasement as a hedge against both despair and backsliding. In so doing, he fails to appreciate the availability and the suitability of an alternative ‘racial realist’ (and tragicomic) posture vis-à-vis American liberalism inspired by thinkers like Ralph Ellison, James Baldwin and Derrick Bell. This alternative enables racially conscious Americans to respond to the intransigence of (certain) white Americans with cunning rather than by escaping into fantasies of a ‘dream country’ unmarked by the damage caused by racism and its long-lingering effects. I uncover and explore this alternative through Rorty’s warnings regarding the white middle class, a somewhat surprising consistency between Rorty’s brand of class politics and Bell’s understanding of ‘racial fortuity’, and, finally, through a development of Bell’s ‘racial realist’ posture combined with Baldwin’s ‘uses of the blues’ resulting in a ‘hard-eyed’ tragicomic sensibility sufficient to effectively pair continued struggle with creative consolation and resilience. (shrink)

Peter Abelard (1079–1142 ce) was the most wide‐ranging philosopher of the twelfth century. He quickly established himself as a leading teacher of logic in and near Paris shortly after 1100. After his affair with Heloise, and his subsequent castration, Abelard became a monk, but he returned to teaching in the Paris schools until 1140, when his work was condemned by a Church Council at Sens. His logical writings were based around discussion of the “Old Logic”: Porphyry's Isagoge, aristotle'S Categories and (...) On Interpretation and boethius'S textbook on topical inference. They comprise a freestanding Dialectica (“Logic”; probably c.1116), a set of commentaries (known as the Logica [Ingredientibus], c. 1119) and a later (c. 1125) commentary on the Isagoge (Logica Nostrorum Petititoni Sociorum or Glossulae). In a work Abelard called his Theologia, issued in three main versions (between 1120 and c.1134), he attempted a logical analysis of trinitarian relations and explored the philosophical problems surrounding God's claims to omnipotence and omniscience. The Collationes (“Debates,” also known as “Dialogue between a Christian, a Philosopher and a Jew”; probably c.1130) present a rational investigation into the nature of the highest good, in which the Christian and the Philosopher (who seems to be modeled on a philosopher of pagan antiquity) are remarkably in agreement. The unfinished Scito teipsum (“Know thyself,” also known as the “Ethics”; c.1138) analyses moral action. (shrink)

On Philosophy and Philosophers is a volume of unpublished philosophical papers by Richard Rorty, a central figure in late-twentieth-century intellectual debates and a primary force behind the resurgence of American pragmatism. The first collection of new work to appear since his death in 2007, these previously unseen papers advance novel views on metaphysics, ethics, epistemology, philosophical semantics and the social role of philosophy, critically engaging canonical and contemporary figures from Plato and Kant to Kripke and Brandom. This book's (...) diverse offerings, which include technical essays written for specialists and popular lectures, refine our understanding of Rorty's perspective and demonstrate the ongoing relevance of the iconoclastic American philosopher's ground-breaking thought. An introduction by the editors highlights the papers' original insights and contributions to contemporary debates. (shrink)

Hampshire has chosen twelve articles to represent recent thought on the philosophy of mind. The selection covers articles in a variety of topics including the mind-body problem, emotion, desire, and the "private language" controversy. The selection is notable in that Hampshire has intentionally chosen articles which suggest the relevance of much of the analytic work on the philosophy of mind to questions of ethics and moral psychology. Among the authors represented in the anthology are D. F. Pears, Wilfrid Sellars, G. (...) E. M. Anscombe, Richard Rorty, and H. H. Price. The volume merits comparison with the anthologies of Chappell, Gustavson, and Anderson, and is a worthwhile complement to them.—A. W. W. (shrink)

The author argues that Thomas Hobbes anticipates a set of questions about meaning and semantic order that come to fuller expression in the 20th century, in the writings of W.V.O. Quine, Ludwig Wittgenstein, Donald Davidson, Jacques Derrida, and Richard Rorty. Despite their different points of departure, these 20th-century writers pose a number of profound questions about the conditions for the stability of meaning, and about the conditions that govern the use of the term “language” itself. Though the more (...) recent debate benefits from a set of philosophical tools unavailable in the seventeenth century, the author further argues that Hobbes performs a number of maneuvers in his texts from which his 20th-century successors would profit. (shrink)

Throughout much of his long life, Kenneth Burke was recognized as a leading American intellectual, perhaps the most significant critic writing in English since Coleridge. From about 1950 on, rhetoricians in both English and speech began to see him as a major contributor to the New Rhetoric. But despite Burke's own claims to be writing philosophy and some notice from reviewers and critics that his work was philosophically significant, Timothy W. Crusius is the first to access his work as philosophy. (...) Crusius traces Burke's commitment and contributions to philosophy prior to 1945, from Counter-Statement through The Philosophy of Literary Form. While Burke might have been a late modernist thinker, Crusius shows that Burke actually starts from a position closely akin to such postmodern figures as Michel Foucault and Richard Rorty. Crusius then examines Burke's work from A Grammar of Motives up to his last published essays, drawing most heavily on A Rhetoric of Motives, The Rhetoric of Religion, and uncollected essays from the 1970s. This part concerns Burke's contributions to human activities always closely associated with rhetoric-hermeneutics, dialectic, and praxis. Burke's highly developed notion of our species as the "symbol-using animal," argues Crusius, draws together the various strands of his later philosophy—his concern with interpretation, with dialectic and dialogue, with a praxis devoted to awareness and control of the self-deceiving and potentially self-destructive motives inherent in language itself. (shrink)

Paul Gewirtz has suggested that contemporary Chinese society lacks a shared framework. A Rortian might describe this by saying that China lacks a “final vocabulary” of “thick terms” with which to resolve ethical disagreements. I briefly examine the strengths and weaknesses of Confucianism and Legalism as potential sources of such a final vocabulary, but most of this essay focuses on Zhuangzian Daoism. Zhuangzi 莊子 provides many stories and metaphors that can inspire advocates of political pluralism. However, I suggest that Zhuangzi (...) is ultimately an “ironist” in Rorty’s sense. Many intellectuals assume there is something progressive and liberating about broadly ironic stances like relativism and skepticism. Ethically, though, irony is “the night in which all cows are black”: since it regards all positions as equally undermined, an ironic stance cannot be enlisted in support of tolerance or humanitarianism or in opposition to absolutism or cruelty. (shrink)

Tragedy and Citizenship provides a wide-ranging exploration of attitudes toward tragedy and their implications for politics. Derek W. M. Barker reads the history of political thought as a contest between the tragic view of politics that accepts conflict and uncertainty, and an optimistic perspective that sees conflict as self-dissolving. Drawing on Aristotle's political thought, alongside a novel reading of the Antigone that centers on Haemon, its most neglected character, Barker provides contemporary democratic theory with a theory of tragedy. He sees (...) Hegel's philosophy of reconciliation as a critical turning point that results in the elimination of citizenship. By linking Hegel's failure to address the tragic dimensions of politics to Richard Rorty, John Rawls, and Judith Butler, Barkeroffers a major reassessment of contemporary political theory and a fresh perspective on the most urgent challenges facing democratic politics. Derek W. M. Barker is a program officer at the Kettering Foundation. (shrink)

It is commonly held that there is no place for the 'now’ in physics, and also that the passing of time is something subjective, having to do with the way reality is experienced but not with the way reality is. Indeed, the majority of modern theoretical physicists and philosophers of physics contend that the passing of time is incompatible with modern physical theory, and excluded in a fundamental description of physical reality. This book provides a forceful rebuttal of such claims. (...) In successive chapters the author explains the historical precedents of the modern opposition to time flow, giving careful expositions of matters relevant to becoming in classical physics, the special and general theories of relativity, and quantum theory, without presupposing prior expertise in these subjects. Analysing the arguments of thinkers ranging from Aristotle, Russell, and Bergson to the proponents of quantum gravity, he contends that the passage of time, understood as a local becoming of events out of those in their past at varying rates, is not only compatible with the theories of modern physics, but implicit in them. (shrink)

In Minkowski spacetime, because of the relativity of simultaneity to the inertial frame chosen, there is no unique world-at-an-instant. Thus the classical view that there is a unique set of events existing now in a three dimensional space cannot be sustained. The two solutions most often advanced are that the four-dimensional structure of events and processes is alone real, and that becoming present is not an objective part of reality; and that present existence is not an absolute notion, but is (...) relative to inertial frame; the world-at-an-instant is a three dimensional, but relative, reality. According to a third view, advanced by Robb, Capek and Stein, what is present at a given spacetime point is, strictly speaking, constituted by that point alone. I argue here against the first of these views that the four-dimensional universe cannot be said to exist now, already, or indeed at any time at all; so that talk of its existence or reality as if that precludes the existence or reality of the present is a non sequitur. The second view assumes that in relativistic physics time lapse is measured by the time co-ordinate function; against this I maintain that it is in fact measured by the proper time, as I argue by reference to the Twin Paradox. The third view, although formally correct, is tarnished by its unrealistic assumption of point-events. This makes it susceptible to paradox, and also sets it at variance with our normal intuitions of the present. I argue that a defensible concept of the present is nonetheless obtainable when account is taken of the non-instantaneity of events, including that of conscious awareness, as that region of spacetime comprised between the forward lightcone of the beginning of a small interval of proper time t and the backward lightcone of the end of that interval. This gives a serviceable notion of what is present to a given event of short duration, as well as saving our intuition of the “reality” or robustness of present events. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Eve W. Stoddard REASON ON TRIAL: LEGAL METAPHORS IN THE CRITIQUE OF PURE REASON 6 6 r I 1WO things fill the mind with ever new and increasing admi_I_ ration and awe, the oftener and more steadily we reflect on them: the starry heavens above me and the moral law within me." ' These are perhaps Kant's most well-known and oft-repeated words. They reflect not only the profound feeling (...) that underlies his technical and abstruse treatises, but also his characteristic preoccupation with law. The "starry heavens" are a synecdoche both for the wonder of nature as we perceive it in all its multiplicity, and for the marvel of science's ability to reduce, order, and subdue that infinite multiplicity into a few elegant laws. These two types of law, natural and moral, define the focus of Kant's critical philosophy, and metaphors drawn from jurisprudence pervade all three critiques. In the context of controversial statements on the role of metaphor in philosophical texts by Jacques Derrida, Paul Ricoeur, and Richard Rorty, I will analyze the legal metaphors in the prefaces and Transcendental Deductions of the Critique ofPure Reason. My goal in engaging Kant's texts in this controversy over metaphor is twofold: on the one hand to assess experimentally the value of these positions on metaphor in the history of philosophy, and, on the other hand, to examine the relations between critical conceptualization and insurgent metaphoricity in Kant's carefully elaborated and systematized text. In a textwhose key words are "universal and necessary for all possible experience," contingentand ambiguous metaphors might be expected to cause problematic unravelings. Richard Rorty has argued recently that "the history ofscience, culture and politics" should be viewed "as a history of metaphor rather than of discovery." 2 He compares the creations of new vocabularies to the 245 246Philosophy and Literature invention of "new tools" ("CL," p. 5), alluding to "Nietzsche's definition of truth as a mobile army of metaphors" (p. 6). From Plato's figures of the world as cave and the mind as charioteer with unruly horses, we shift to Locke's view of mind as tahda rasa and Descartes's description of the world as a machine. Rorty's paradigm of cultural history as a history of metaphor enters into an earlier, unresolved debate between Jacques Derrida and Paul Ricoeur over the relationship between metaphor and philosophical discourse. Like Derrida, Rorty follows Nietzsche's claims about metaphor in the history of philosophy, a view Ricoeur wants to disprove so that he can recover the privileged univocity of speculative discourse. However Rorty has nothing in common with die complexity and "invaginated" ambiguities, the dazzling multivocity of Derrida's writing on the economics of metaphor. Although Rorty appears at first to agree with Derrida that there is no truth or reality apart from the linguistic tropes which dominate different epochs and cultures, he retains a metaphysical distinction between literal reference and figurative play. Rorty adopts Donald Davidson's theory that metaphors do not have "meaning" precisely because diey have no place in the language game into which they are inserted. They produce an effect, but it is not meaning: "One can only savour it or spit it out"; it is not a " 'truth-value candidate' " ("CL," p. 6). However, through repeated use, the metaphor will find a role in the language game; dying as a metaphor, it will live as a literal statement. Therefore Rorty agrees with Ricoeur that a moribund metaphor is no longer a metaphor, but a literally functioning segment of discourse. Thus despite his initial move toward a Derridean, or atleast Nietzschean, position, Rorty ultimately takes a stand consonant with Ricoeur's desire to rescue speculative discourse from the unruliness of metaphor. Considering Rorty's celebration of Freud in an article on "The Contingency of Selfhood," 3 his failure to consider the role of unconscious associations and overdetermination in the writing and reading of texts is surprising. Dead or alive, a metaphor brings with it a host ofpersonal and public, conscious and unconscious, new and traditional associations that become juxtaposed against a similar number of associations connected with the signifying chain into which the metaphor has been inserted. In... (shrink)

In the transition to Einstein’s theory of Special Relativity (SR), certain concepts that had previously been thought to be univocal or absolute properties of systems turn out not to be. For instance, mass bifurcates into (i) the relativistically invariant proper mass m0, and (ii) the mass relative to an inertial frame in which it is moving at a speed v = βc, its relative mass m, whose quantity is a factor γ = (1 – β2) -1/2 times the proper mass, (...) m = γm0. (shrink)

It is well known that Leibniz advocated the actual infinite, but that he did not admit infinite collections or infinite numbers. But his assimilation of this account to the scholastic notion of the syncategorematic infinite has given rise to controversy. A common interpretation is that in mathematics Leibniz’s syncategorematic infinite is identical with the Aristotelian potential infinite, so that it applies only to ideal entities, and is therefore distinct from the actual infinite that applies to the actual world. Against this, (...) I argue in this paper that Leibniz’s actual infinite, understood syncategorematically, applies to any entities that are actually infinite in multitude, whether numbers, actual parts of matter, or monads. It signifies that there are more of them than can be assigned a number, but that there is no infinite number or collection of them, which notion involves a contradiction. Similarly, to say that a magnitude is actually infinitely small in the syncategorematic sense is to say that no matter how small a magnitude one takes, there is a smaller, but there are no actual infinitesimals. In geometry one may calculate with expressions apparently denoting such entities, on the understanding that they are fictions, standing for variable magnitudes that can be made arbitrarily small, so as to produce demonstrations that there is no error in the resulting expressions. (shrink)

This book is part of Prentice-Hall's new Central Issues in Philosophy series, and seems a welcome addition. The editor's introduction does little more than state the problem and review some of the ways with which it has been dealt. We are then brought immediately to the meat: the first section of the book contains selections from Descartes, Spinoza, and Hobbes intended to acquaint us with some of the more classical solutions to the problem. The second part, entitled "The Identity Thesis," (...) contains one of J. J. C. Smart's influential essays for this thesis and two replies, one by Jerome Shaffer and one by James Cornman. Part three, entitled "Theoretical Materialism," contains essays by Jaegwon Kim, in which he denies the validity of having only physical property descriptions; and Thomas Nagel and Keith Gunderson, who both argue that the case for materialism is stronger than the case against it. The fourth part, containing essays by Jerry Fodor, Hilary Putnam, and David Lewis, focuses on functional materialism. The fifth section of the book is devoted to the rather radical view of the eliminative materialists. There is a short note by Paul Feyerabend, a full length essay by Richard Rorty, a reply by Richard Bernstein and a rejoinder by Rorty. All of the essays in this book are well-written pieces of solid philosophy, but none is so technical that it can not be understood by a relative beginner. After finishing this book and thoroughly digesting its contents, the reader will be well versed in modern thought on this problem and well capable of continuing his research in any of several directions. To aid the student in this task there is a large bibliography included.--W. de V. (shrink)

This volume contains essays that examine infinity in early modern philosophy. The essays not only consider the ways that key figures viewed the concept. They also detail how these different beliefs about infinity influenced major philosophical systems throughout the era. These domains include mathematics, metaphysics, epistemology, ethics, science, and theology. Coverage begins with an introduction that outlines the overall importance of infinity to early modern philosophy. It then moves from a general background of infinity up through Kant. Readers will learn (...) about the place of infinity in the writings of key early modern thinkers. The contributors profile the work of Descartes, Spinoza, Leibniz, and Kant. Debates over infinity significantly influenced philosophical discussion regarding the human condition and the extent and limits of human knowledge. Questions about the infinity of space, for instance, helped lead to the introduction of a heliocentric solar system as well as the discovery of calculus. This volume offers readers an insightful look into all this and more. It provides a broad perspective that will help advance the present state of knowledge on this important but often overlooked topic. (shrink)

The quantum theory of atoms in molecules (QTAIM) uses physics to define an atom and its contribution to observable properties in a given system. It does so using the electron density and its flow in a magnetic field, the current density. These are the two fields that Schrödinger said should be used to explain and understand the properties of matter. It is the purpose of this paper to show how QTAIM bridges the conceptual gulf that separates the observations of chemistry (...) from the realm of physics and do so in a manner that is both rigorous and conceptually simple. Since QTAIM employs real measurable fields, it enables one to present the findings of complex quantum mechanical calculations in a pictorial manner that isolates the essential physics. The time has arrived for a sea change in our attempts to predict and classify the observations of chemistry, time to replace the use of simplified and arbitrary models with the full predictive power of physics, as applied to an atom in a molecule. (shrink)

Before establishing his mature interpretation of infinitesimals as fictions, Gottfried Leibniz had advocated their existence as actually existing entities in the continuum. In this paper I trace the development of these early attempts, distinguishing three distinct phases in his interpretation of infinitesimals prior to his adopting a fictionalist interpretation: (i) (1669) the continuum consists of assignable points separated by unassignable gaps; (ii) (1670-71) the continuum is composed of an infinity of indivisible points, or parts smaller than any assignable, with no (...) gaps between them; (iii) (1672- 75) a continuous line is composed not of points but of infinitely many infinitesimal lines, each of which is divisible and proportional to a generating motion at an instant (conatus). In 1676, finally, Leibniz ceased to regard infinitesimals as actual, opting instead for an interpretation of them as fictitious entities which may be used as compendia loquendi to abbreviate mathematical reasonings. (shrink)

In this paper, we endeavour to give a historically accurate presentation of how Leibniz understood his infinitesimals, and how he justified their use. Some authors claim that when Leibniz called them “fictions” in response to the criticisms of the calculus by Rolle and others at the turn of the century, he had in mind a different meaning of “fiction” than in his earlier work, involving a commitment to their existence as non-Archimedean elements of the continuum. Against this, we show that (...) by 1676 Leibniz had already developed an interpretation from which he never wavered, according to which infinitesimals, like infinite wholes, cannot be regarded as existing because their concepts entail contradictions, even though they may be used as if they exist under certain specified conditions—a conception he later characterized as “syncategorematic”. Thus, one cannot infer the existence of infinitesimals from their successful use. By a detailed analysis of Leibniz’s arguments in his De quadratura of 1675–1676, we show that Leibniz had already presented there two strategies for presenting infinitesimalist methods, one in which one uses finite quantities that can be made as small as necessary in order for the error to be smaller than can be assigned, and thus zero; and another “direct” method in which the infinite and infinitely small are introduced by a fiction analogous to imaginary roots in algebra, and to points at infinity in projective geometry. We then show how in his mature papers the latter strategy, now articulated as based on the Law of Continuity, is presented to critics of the calculus as being equally constitutive for the foundations of algebra and geometry and also as being provably rigorous according to the accepted standards in keeping with the Archimedean axiom. (shrink)

In preparation for his lectures on Leibniz delivered in Cambridge in Lent Term 1899, Russell started in the summer of 1898 to keep notes on writings by and about Leibniz in a large notebook of the type he commonly used for notetaking at this time. This article prints, with annotation, all the material on Leibniz in that notebook.

In lively and readable prose, Arthur presents a new approach to the study of logic, one that seeks to integrate methods of argument analysis developed in modern “informal logic” with natural deduction techniques. The dry bones of logic are given flesh by unusual attention to the history of the subject, from Pythagoras, the Stoics, and Indian Buddhist logic, through Lewis Carroll, Venn, and Boole, to Russell, Frege, and Monty Python. A previous edition of this book appeared under the title _Natural (...) Deduction_. This new edition adds clarifications of the notions of explanation, validity and formal validity, a more detailed discussion of derivation strategies, and another rule of inference, Reiteration. (shrink)

In this paper I try to sort out a tangle of issues regarding time, inertia, proper time and the so-called “clock hypothesis” raised by Harvey Brown's discussion of them in his recent book, Physical Relativity. I attempt to clarify the connection between time and inertia, as well as the deficiencies in Newton's “derivation” of Corollary 5, by giving a group theoretic treatment original with J.-P. Provost. This shows how both the Galilei and Lorentz transformations may be derived from the relativity (...) principle on the basis of certain elementary assumptions regarding time. I then reflect on the implications of this derivation for understanding proper time and the clock hypothesis. (shrink)

In this paper I attempt to throw new light on Leibniz's apparently conflicting remarks concerning the continuity of matter. He says that matter is "discrete" yet "actually divided to infinity" and (thus dense), and moreover that it fills (continuous) space. I defend Leibniz from the charge of inconsistency by examining the historical development of his views on continuity in their physical and mathematical context, and also by pointing up the striking similarities of his construal of continuity to the approach taken (...) by 20th century Combinatorial Topology. (shrink)

Richard Arthur’s _Natural Deduction_ provides a wide-ranging introduction to logic. In lively and readable prose, Arthur presents a new approach to the study of logic, one that seeks to integrate methods of argument analysis developed in modern “informal logic” with natural deduction techniques. The dry bones of logic are given flesh by unusual attention to the history of the subject, from Pythagoras, the Stoics, and Indian Buddhist logic, through Lewis Carroll, Venn, and Boole, to Russell, Frege, and Monty Python.

In lively and readable prose, Arthur presents a new approach to the study of logic, one that seeks to integrate methods of argument analysis developed in modern “informal logic” with natural deduction techniques. The dry bones of logic are given flesh by unusual attention to the history of the subject, from Pythagoras, the Stoics, and Indian Buddhist logic, through Lewis Carroll, Venn, and Boole, to Russell, Frege, and Monty Python. A previous edition of this book appeared under the title _Natural (...) Deduction_. This new edition adds clarifications of the notions of explanation, validity and formal validity, a more detailed discussion of derivation strategies, and another rule of inference, Reiteration. (shrink)

In lively and readable prose, Arthur presents a new approach to the study of logic, one that seeks to integrate methods of argument analysis developed in modern “informal logic” with natural deduction techniques. The dry bones of logic are given flesh by unusual attention to the history of the subject, from Pythagoras, the Stoics, and Indian Buddhist logic, through Lewis Carroll, Venn, and Boole, to Russell, Frege, and Monty Python. A previous edition of this book appeared under the title _Natural (...) Deduction_. This new edition adds clarifications of the notions of explanation, validity and formal validity, a more detailed discussion of derivation strategies, and another rule of inference, Reiteration. (shrink)