Robert C. Koons Realism Regained an Exact Theory of Causation, Teleology, And the Mind 2000

REALISM REGAINED

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Realism Regained An Exact Theory of Causation, Teleology, and the Mind

ROBERT C.KOONS

OXFORD UNIVERSITY PRESS 2000

OXFORD UNIVERSITY PRESS Oxford NewYork Athens Auckland Bangkok Bogota Buenos Aires Calcutta Cape Town Chennai Dares Salaam Delhi Florence Hong Kong Istanbul Karachi Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi Paris Sao Paulo Singapore Taipei Tokyo Toronto Warsaw and associated companies in Berlin Ibadan

Copyright©2000 by Robert C.Koons Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Koons, RobertC. Realism regained: an exact theory of causation, teleology, and the mind Robert C. Koons p. cm. Includes bibliographical references and index. ISBN 0-19-513567-9 1. Causation. 1. Title. BD541.K66 2000 122—dc21 99-054666

9 8 7 6 5 4 3 2 1 Printed in the United States of America on acid-free paper

In memory of Jon Barwise, friend and mentor

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Preface Causation, the relation of cause to effect, has long been recognized as one of the most central subjects in philosophy. After a period of relative neglect during the era of logical positivism, the late twentieth century has seen a renaissance of interest in causation, as one philosopher after another provides a "causal theory" of this or that phenomenon: reference and meaning, identity and duration, perception and knowledge, information and representation. At the same time, the development of the formal disciplines, including modal logic (the logic of possibility and necessity), probability theory, mereology (the theory of parts and wholes), defeasible or "nonmonotonic" logics (developed in the field of artificial intelligence to represent commonsense inference), and partial semantics (most prominently, the situation theory of Barwise, Perry, and Etchemendy), has provided the tools needed for an exact and comprehensive theory of causation. Up to this point, formal accounts of causation have followed the empiricist strictures laid down by David Hume. These accounts of causation force the concept into the periphery (making the concept of causation dependent on our prior understanding of such theoretical machinery as spatiotemporal location, subjunctive conditionals, experience, and empirical knowledge) and consequently do not mesh with the causal theories that have become so popular in epistemology and the philosophy of mind, which, by contrast, require causation to play a central and non-derivative role. In this book, I construct a non-Humean or realist theory of causation (employing the technical tools mentioned in the preceding paragraph), and I show how this account sheds light on existing causal theories and their outstanding problems. In the process, I sketch a metaphysical theory that employs relatively few primitive elements and comprises a well-understood mathematical theory of these elements and a precise account, in terms of these elements, of a wide variety of phenomena, drawn both from our common experience and scientific knowledge. These phenomena include information, teleology and biological function, mental representation, qualia and mental causation, our knowledge of logic, mathematics, and theoretical science, the structure of space and time, the identity and duration of physical objects, and the nature and objectivity of ethical values. I offer what could be called a "naturalistic" account of the normative dimension: the standards of correctness and propriety that are essential to our understanding both of intentionality and of ethics. It builds upon and refines

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recent work on the teleological theory of norms on the part of Dretske, Stampe, Millikan, and others. At the same time, the argument of the book is in part directed against a narrowly materialistic ontology. I provide seven independent lines of argument for thinking that we need to recognize the existence of states other than merely physical states; in particular, we must acknowledge the existence of modal facts, including facts of logical, mathematical, and natural necessity. By bringing these modal facts within the scope of causation, I explain how it is possible for us to gain information about them. Consequently, I am able to defend a position that is realist in the sense both of including a version of the traditional correspondence theory of truth and of including an ontology in which mental states, qualia, numbers and sets, objective norms, and modal facts are first-class citizens. Acknowledgment is made to the following publishers for their kind permission to reprint excerpts from: "Teleology as Higher-Order Causation: A Situation-Theoretic Account," Minds and Machines 8 (1998): 559-585. Published by Kluwer Academic Publishers; reprinted on pages 82-90, 95-96, 115-116, 135-143, and 203-215. "Situation-Mereology and the Logic of Causation," Topoi 18 (1999). Published by Kluwer Academic Publishers; reprinted in chapter 3, pages 35-49. "A New Look at the Cosmological Argument," by Robert C. Koons, American Philosophical Quarterly 34 (April 1997), pages 194-199 and 202-207; reprinted in chapter 9, pages 146-159. "Information, Representation and the Problem of Error," by Robert C. Koons, 000000000000000000000000000000000000000000000000000000000000000000 published by the Center for the Study of Language and Information, Stanford, California, 1996, pages 333-345; reprinted in chapter 11, pages 181-184. Work on this book was made possible by a Faculty Research Assignment from the University Research Institute at the University of Texas at Austin, during the spring semester of 1997. I would also like to thank Michael Dunn, the Philosophy Department and the Institute for Advanced Study at Indiana University for their support during my visit in Bloomington during much of that semester. I would also like to thank Anil Gupta, and Gregg Rosenberg, who provided very helpful feedback on early drafts of the book. Jon Barwise provided the inspiration for the formal framework, situation theory, used in this book, and Jon was extraordinarily generous in giving me both his time and his encouragement at the inception of the project. Professor Barwise was one of the most creative and original philosophers of our time. He will be sorely missed. My debt to my teachers, including David Charles at Oriel; Robert M. Adams, David Kaplan, and Tony Martin at UCLA; and, especially, my doctoral supervisor, Tyler Burge, is incalculable. Drafts of several chapters were much improved through discussion with the Naturalism Reading Group at the University of Texas: Daniel Bonevac, Brian Leiter, Cory Juhl, and David Sosa. My colleague Nicholas Asher has played an

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indispensable role in the development of my ideas concerning nonmonotonic inference. Professor T. K. Seung has mentored me throughout my years in Austin and opened my eyes to the contemporary relevance of Plato's later philosophy. Ms. Yi Mao provided very helpful feedback, as did two anonymous referees for Oxford University Press. I would also like to thank my editor, Peter Ohlin, for his perseverance in support of this project. Finally, I thank my wife, Debbie, for her patience and support. Austin, Texas August 1999

R. C. K.

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Contents 1 Introduction

1.1 A Comprehensive Realism 1.2 Metaphysical Method 1.3 An Alternative to Both Physicalism and Mysterianism 1.4 Causal Internalism 1.5 The Ontology of Causation 1.6 The Need for an Indeterministic Model 1.7 A Causal-Probabilistic Theory of Information 1.8 Why an Exact Theory? 1.9 The Big Picture: Preview of Part II 1.10 A Glossary of Symbols

1

1 3 3 4 7 8 9 10 11 14

1 A Theory of Causation and Information 2

Toward a Unified Theory of Causation

2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13

The Nomological/Deductive Tradition Theories of Probabilistic Causation Davidson and Event-Tokens Lewis's Counterfactual Account Mackie's INUS Conditions Yablo's Theory Branching-Time Models Artificial Intelligence and Models of Causal Inference Tooley and Cartwright . . Process and Linkage Theories Mellor's Theory Accounts of Causal Asymmetry Distinctive Features of My Theory

19

20 20 21 21 23 24 25 25 25 26 27 28 29

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3 Situation Theory and Causation 3.1 The Need for Situation Theory 3.2 Situation Mereology and Causation 3.3 A Situation-Theoretic Logic of Causation 3.4 The Transitivity of INUS Causation

31 31 37 39 41

4 A Deterministic Model 4.1 Desiderata 4.2 Causation and Determinism 4.3 Basic Ontology 4.4 Constraints and Causation 4.5 Defining Causal Explanation 4.6 Singular Causation 4.7 Empiricism and Modality 4.8 Causal Relevance 4.9 Piecemeal Causation 4.10 Desirable Features of the Theory 4.11 Applying the Theory to Some Examples 4.12 Verifying the Axioms of Chapter 3

45 45 47 49 55 56 59 61 61 65 65 69 75

5 An 5.1 5.2 5.3 5.4 5.5 5.6

77 77 78 79 81 82 87

Indeterministic Model Beyond Determinism Why an Indeterministic Account Is Difficult If Not Determinism, Then What? Causation and Causal Explanation Desirable Features of the Theory Example Applications

6 A Probabilistic Model of Causation 6.1 Models 6.2 Token Causation 6.3 Weighted Causal Constraints on Types 6.4 Probabilistic Explanation 6.5 Examples 6.6 Humphreys's Explanation 7 Higher-Order Causation: Modal Facts as Causes 7.1 A Problem with Higher-Order Causation 7.2 Modal Facts as Causes 7.3 The Causal Relevance of the Excluded Middle 7.4 First-Order Teleological Causation 7.5 Higher-Order Teleological Causation

91 91 92 92 93 93 97 99 99 101 102 103 105

Contents

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8 The Universality of Causation 8.1 A Modal Mereology of Situations 8.2 Principles of Causation 8.3 The Universality of Causation 8.4 The Existence of an Uncaused First Cause 8.5 The Well-Foundedness of Causation 8.6 Objections

107 108 109 109 110 113 113

9 A Theory of Information and Misinformation 9.1 Introduction 9.2 The Historical (Retrospective) Strategy 9.3 Two New Strategies 9.4 Information as the Basis of Knowledge

121 121 122 124 127

10 A Look Back, and Ahead 10.1 The Causal Relation 10.2 Against Determinism 10.3 Spacetime as Constrained by Causation, Not Vice Versa

129 129 129 130

II Applications to Metaphysics, Epistemology, and Ethics 11 An Overview 11.1 Teleology as Higher-Order Causation 11.2 Teleosemantics 11.3 The Link between Teleosemantics and Epistemology 11.4 Causal/Teleological Accounts of Knowledge 11.5 Mental Causation and Qualia 11.6 Teleological Accounts of Ethics 11.7 Enduring Substances as Logical Constructions

135 135 136

12 Teleology as Higher-Order Causation 12.1 Three Definitions of Teleology 12.2 Darwin: Real or Only Apparent Functionality? 12.3 Retrospective and Non-Retrospective Accounts 12.4 Extrinsic Functions and the Extended Phenotype . 12.5 Our Knowledge of Teleology 12.6 Teleological Natural Kinds

141 141

137 137 138 138 139

149 150 151 152 153

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13 Causal Theories of Mental Content 13.1 Millikan 13.2 Dretske 13.3 Fodor's Critique of Teleological Semantics

155 155 156

14 Teleosemantics of Mental Representations 14.1 An Overview of Representational States 14.2 Pre-cognitive Representations 14.3 Cognitive States: Opinions and Intentions 14.4 Mental Representation and Language 14.5 The Narrowness of Mental Content 14.6 Teleosemantics and the Liar Paradox

161 161 163

15 A Causal Theory of Logical and Mathematical Cognition 15.1 The Need for a Causal Theory 15.2 Logico-Modal Facts as Causes 15.3 Knowing How to Infer Correctly 15.4 Is Logic Factual? 15.5 Logical and Physical Necessity 15.6 From Logic to Arithmetic 15.7 Set Theory and Other Branches of Mathematics 15.8 Alternatives to Mathematical Realism 15.9 Why the Human Mind Is Not a Turing Machine 16 A Teleological Theory of the Mind 16.1 The Irony of Non-Reductive Materialism . . .16.2 Supervenience and Type and Token Identity 16.3 Downward Causation versus Epiphenomenalism 16.4 Two Further Problems of Mental Causation 16.5 Qualia 16.6 Problem Cases 16.7 The Correlation of Qualia and Physiology 16.8 Free Will 17 Teleological Reliabilism 17.1 Reliabilism: The Reference Class Problem

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166 167 168 168 169 169 170 172 173 . 184 185 190 192 194 197 197 198 201 205 206 207 213 213 217 217

Contents 17.2 Grue, Bleen, and the New Riddle of Induction 17.3 Curve-Fitting: The Problem of Mathematical Simplicity 17.4 The Reliability of Simplicity as a Criterion of Truth 17.5 The Incompatibility of Materialism and Scientific Realism 17.6 When Does Bayesian Learning Constitute Knowledge? 17.7 Objective Chance and Empiricism 18 Enduring Substances and Their Identities 18.1 Substances as Logical Constructions 18.2 Change and the Johnston Paradox 18.3 Zeno's Paradox and the Instant of Change 18.4 Hard Cases for Substance Identity 18.5 Quantum Reality and the Foundations of Materialism

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.218 220 221 222 232 234 241 241 244 245 245 249

19 Eudaemonism and the Objectivity of Value 19.1 Objectified Subjectivity: A Dead End 19.2 Eudaemonia 19.3 The Connection between Eudaemonia and Motivation 19.4 Nature and Nurture 19.5 The Unity and Universality of Good 19.6 Indeterminacy and Objectivity 19.7 The Semantics and Epistemology of Ethics 19.8 Eudaemonism versus Evolutionary Ethics 19.9 Moore and the Indefinability of Good

257 257 260

20 Moral Theory as the Teleology of Character 20.1 Virtue as Both Means and End 20.2 Eudaemonism versus Egoism 20.3 Is and Ought 20.4 Sociobiology, Game Theory, and Species Relativity 20.5 Elements of a Teleo-Ethological Morality 20.6 Politics and the Natural Law 20.7 Justice toward Future Generations 20.8 Kierkegaard and the Teleological Suspension of the Ethical

271 271 271 272

260 263 263 265 266 267 268

273 274 274 276 277

xvi 21 A Coherent Realism Is a Comprehensive Realism 21.1 The Four Waves of Anti-Realism 21.2 A Prolegomenon to Any Future Critique of Metaphysics 21.3 Causalism, Yes! Materialism, No! 21.4 Anti-Realist Obscurantism 21.5 Is the Theory Naturalistic? A Partiality, Modality, and Conditionals A.I Partial Prepositional Logics A.2 Partial Modal Logics A.3 Partial Conditional Logics A.4 Partiality and Quantificational Logic A.5 First-Order Quantification over Situation-Types

Realism Regained 279 279 281 282 285 286 289 289 293 297 303 309

B A Causal Calculus B.I Causation and Projectible Statistics B.2 Some Other Well-Known Puzzles B.3 Screening Off B.4 Conditions on Hyperfinite Probability Functions B.5 Examples B.6 Abduction and Induction B.7 Proofs of Theorems B.2 through B.4

311 311 313 314

Bibliography

329

Index

341

316 320 323 324

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1 Introduction Physicists are currently searching for what they call a "theory of everything." However, it turns out that the "everything" they have in mind falls far short of every thing. The physicists' theory of everything has nothing to say about mental phenomena, agency, values, norms, teleology, or intentionality, to mention but a few. In fact, physicists rarely have much to say about the natures of the fundamental elements of their theory: particles, fields, space, and time. None of this is surprising, and none of it is a criticism of current physics as such. When physicists refer to a coming "theory of everything," they do so (or, at least, the sophisticated ones do so) with tongue in cheek. It is metaphysics, and not physics, whose province it is to fashion a theory of everything. This book is a work in real, honest-to-God, no-apologies-given metaphysics, but metaphysics conducted in a thoroughly scientific spirit. My hope is that it will help to stimulate a return to the perennial concerns of philosophy.

1.1

A Comprehensive Realism

A class of propositions can be interpreted realistically when two conditions are met: 1. Some of the propositions are evaluated as true or false. 2. The truth or falsity of the propositions in the class is determined by some set of facts, and this set of facts plays an indispensable role in explaining our knowledge of the truth or falsity of the propositions in the class. The first condition is not sufficient, since the truth values of the propositions could be determined by facts about our collective acts of affirmation or projection, in which case the propositions could not be interpreted realistically. The causal element introduced by the second condition is critical, because it specifies a direction of asymmetric dependence: our knowledge depends causally on the fact establishing the truth or falsity of the corresponding propositions. This entails that the facts determining these truth conditions do not include facts about 1

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our attitude toward those very propositions, since causal dependency cannot be circular. I will argue that propositions involving reference to the following things can and should be interpreted realistically: • Natural properties and relations • Situation and event tokens • Modality and objective probability • Causal connections • Numbers • Proper functions (teleofunctions) • Mental states • Secondary qualities • Enduring substances • Values and norms Although my position is one of a comprehensive realism, I give a relatively simple and unified picture of the world. The first three items on the list above are treated as primitives, but all of the others are explicated in terms of these more fundamental entities, properties, and relations. Everything that is posited to exist is posited to exist because of some role it plays in the causal network of the world. My approach is resolutely non-dualistic: I reject any sort of Cartesian or neo-Cartesian postulation of a scientifically inaccessible realm of subjectivity. At the same time, I do not start with any a priori or dogmatic requirement. My aim has not been to build a theory of the mind that is materialistic or physicalistic or naturalistic. To begin one's metaphysical inquiry with such dogmatic commitments is methodologically irresponsible. We must simply follow the evidence where it leads. If it leads to materialism, well and good, but if it leads away from it (as my own account does in several respects), we must be willing to be accountable to the facts, not to philosophical fashion. Theories of content, meaning, and representation in terms of causal connection have become very prevalent. A number of philosophers have taken causal theories of content as reason to be anti-realist about values (Mackie, Harman), numbers (Field), and minds (the Churchlands). In my view, the burden of such anti-realism is too great for a theory of content to bear. However, if a causal theory of content could be devised that vindicated realism about values, numbers, and minds, such a theory would give us the best of both: a plausible, informative, and simple account of content, and the accommodation of much of our commonsense view of the world. In this book, I will try to develop such a theory.

Introduction

1.2

3

Metaphysical Method

This book is unapologetically a work of substantive metaphysical theory. Fortunately, blind anti-metaphysical prejudice is not as common as it once was. Nonetheless, many may legitimately ask for the ground rules of the enterprise. In a recent book on causation, Daniel Hausman (1998) proposed five criteria for evaluating metaphysical theories: 1. Intuitive fit 2. Empirical adequacy, consistency with what we know about the world, including our best scientific knowledge 3. Epistemic access — the theory should include some account of how we could come to know its truth 4. Superseding competitors — the theory should incorporate the successes of its predecessors 5. Metaphysical fecundity — the theory should shed light on a variety of metaphysical issues The only criterion that I would add to the list is that of simplicity or elegance. A good metaphysical theory should not be in need of ad hoc rescues or endless epicyclic tinkering. The principal motivation of my work is that of unification. I aim to provide a unified account of intentionality and knowledge, one in which we give exactly the same kind of account both for our thought about and knowledge of objects and events in space and time, and for our thought about and knowledge of the facts of logic, mathematics, laws of nature, and objective chance. We should not accept a bifurcated, disjunctive account of thought and of knowledge so long as a unified account is possible. The theoretical cost of postulating genuine modal facts (as I do) is small in comparison to the benefits of unification.

1.3

An Alternative to Both Physicalism and Mysterianism

Since causal relations play the fundamental role in my metaphysics, the term "causalism" might be an appropriate term for my approach. In recent years, others have taken what could be described as an essentially causalist approach to the metaphysics of mind, namely Armstrong, Millikan, Dretske, Papineau, and Lycan. A causalist theory of mind identifies intentionality with a certain kind of causal property (perhaps involving higher-order causal connections), and the peculiar qualities of conscious experience are taken to be explicable in terms of their intentionality. In all of these cases, causalism is seen as a strategy for defending materialism against various objections concerning intentionality and consciousness. The opponents of these approaches, including Searle and

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McGinn, have been labeled the "mysterians," since they hold that we can expect to find no informative account of the nature of intrinsic intentionality or consciousness. Unfortunately, those participating in these controversies have overlooked the fact that causalism is separable from a commitment to physicalism or materialism. A non-physicalist causalism would include an informative account of the nature of mental states without insisting that everything can ultimately be explained in terms of atoms and the void. I will argue that all of the extant objections to causalist theories of mind are in reality objections to the conjunction of causalism with physicalism. A non-physicalist causalism provides the resources for an adequate answer to these objections. In addition, I will argue that there are independent grounds, having nothing to do with the philosophy of mind, for rejecting physicalism.

1.4

Causal Internalism

The notion of causality is absolutely central to recent philosophical work in semantics, the philosophy of mind and intentionality, epistemology, and philosophy of science. Work by Donnellan, Kripke (1980), and Putnam (1975) helped to make causal connections an indispensable part of our accounts of reference and signification. This in turn has generated causal theories of information and content by Dretske (1981), Fodor (1990), and others. The Gettier problem led to the renaissance of causal theories of knowledge by Goldman (1979), Armstrong (1968), Pollock (1986), and Plantinga (1993). Causality is put to much work in recent theories of personal identity and of the nature of mental states (as in the functionalism of Lewis (1986b) and Putnam (1975)). Causation continues to figure prominently in philosophy of science — e.g., Wesley Salmon's causal theory of evidence (Salmon (1984)) — and in theoretical science, both within physics and outside. Additionally, causal reasoning plays a central role in both understanding and predicting events. Recent work in artificial intelligence has brought causal reasoning into renewed prominence. For example, the much-discussed Yale Shooting Problem reveals (according to most diagnoses; see especially Pearl (1988)) the absolute necessity of recording and using information about the causal links between the bits of information we have about the world. Attempts to explain away causation or to replace it with some purely statistical regularity (whether or not supplemented by some kind of psychologistic decoration) have proved to be catastrophic failures. Every attempt to explain causal direction (surely one of the most fundamental features of causality) in terms of the nomological-deductive model has failed. Such models of causality have generated paradoxes far more rapidly than ad hoc solutions can be invented for them. If a robust sense of reality leads us to recognize causal connections as firstclass citizens of our ontological inventory, we must also make room for those special kinds of objects that can serve as relata for causal relations, whether

Introduction

5

we call these objects possible 'facts', 'situations', or 'states of affairs'. These objects must be distinguished from propositions and from quasi-linguistic representations if we are to capture accurately the logical relations governing causal idioms. The restoration of such fact-like entities to respectability has also been a common theme of recent work in philosophy, including philosophical linguistics and the Stanford situation theory of Barwise and Perry (1983). The project of building a unified theory of intentionality and knowledge in causal (or teleo-causal) terms faces a major obstacle: accounting for our knowledge of modal facts, i.e., facts about necessity and possibility (including logical and mathematical modality), about counterfactual conditionals, about objective chance or propensity (as a generalization of objective modality), and about physical or natural necessity as embodied in natural laws. This obstacle is a generalization of the problem Paul Benacerraf (Benacerraf (1983a), Benacerraf (1983b)) has raised in the case of mathematics: how is definite reference to and substantive knowledge about mathematical objects possible, given that our best theories of reference and knowledge involve causal connections between our thoughts and their targeted aspects of reality? Benacerraf's problem generalizes to our thought about the laws of nature, about the objective chances of certain kinds of events in certain situations, and about various kinds of possibility and necessity. In each case, we seem to have intentional reference to and knowledge of things that the philosophical tradition has long considered to be causally inert. Overcoming this obstacle calls for a revolutionary rethinking of our standard picture of causation. This standard picture I call the horizontal or externalist model of causation. The alternative I am proposing is the thesis of causal internalism, which countenances the reality of vertical causation. On the standard, horizontal model, causes and effects are, exclusively, physical, spatiotemporally local states and occurrences. The causal nexus, whether it consists in a kind of necessary, stochastic, or nomic connection, stands outside of both the cause and the effect. This is why I call it causal externalism: the causal nexus is wholly external to both the cause and the effect. The horizontal/externalist model can account for our knowledge of occurrent properties realized in spatiotemporal locations, but it leaves the entire realm of modality causally, and, therefore, cognitively and epistemically, inaccessible. My alternative proposal is that we consider the modal (or nomic or stochastic) facts that tie the cause to the effect to be internal to the cause or to the effect. Depending on the details of one's account of causation, causes necessitate or probabilify or possibility their effects. On an internalist model, the fact that a given cause necessitates its effect is itself an integral part of the total cause, not something that stands outside or above the cause-effect pair. Consequently, modal facts are every bit as causally efficacious as are occurrent physical facts, and so there is no barrier to providing a unified, causal theory of all of human thought and knowledge. For instance, we can think about and gain knowledge of natural laws by virtue of the fact that each of these laws enters into some, but not all, causal connections. When we observe a regularity (like the elliptical orbits of the planets) that is really caused by a particular nomic fact (like

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the law of gravitation), then our observations provide us with intentional and epistemic contact with that nomic fact. Here are some of the more significant claims that I make in part I concerning the nature of causation: 1. The causal nexus is not something above and outside the cause and effect but consists of facts wholly internal to the cause and the effect. This thesis of causal internalism commits me to the existence of vertical causation from modal and nomic facts to ordinary spatiotemporal ones, crucial to giving a unified, causal account of intentionality and knowledge. 2. Modal facts exist, including facts of logical and mathematical necessity, and these facts are not reducible to or supervenient on the occurrent facts of the world (including its merely actual regularities). The existence of logical types (negations, conjunctions, disjunctions, etc.) of arbitrary complexity is a substantive fact about the world. 3. There are compelling reasons for rejecting a strong version of determinism, reasons that are independent of the problem of free will (chapters 4 and 5). 4. Only actual situations exist, but in constructing models for modal logic, it is convenient to introduce the fiction of merely possible and even impossible situations. 5. I propose a new solution to the problem of the scope or extent of causation, namely, that every wholly contingent state has a cause. On the basis of this principle, I demonstrate the existence of a necessary first cause (chapter 8). 6. It is possible to give a principled basis for a defeasible or nonmonotonic logic that incorporates causal information. This logical calculus (developed in appendix B) generates rich and plausible conclusions about probable consequences of known or hypothesized states. My theory of causation is designed to provide an exact, mathematical model that satisfies the following aims: 1. Causal connections and order should be defined without reference to space and time, permitting the construction of a non-circular, causal theory of spacetime. 2. It should permit the possibility of higher-order or vertical causal connections, in order to explain logical and mathematical knowledge, mind/body interaction, and the nature of teleofunctions. 3. It should provide natural explanations of the formal properties of causation and causal explanation, including transitivity, asymmetry, and veridicality.

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4. It should match the data provided by intuitions about the validity and invalidity of various forms of causal reasoning. In particular, it should explain the failure of substitution of classical equivalents in causal contexts (see chapter 3), and our default assumption of the universality of causal explanation (chapter 8). 5. It should be able to navigate successfully through the complexities of the relationship between causality on the one hand, and modal and statistical relations on the other. It should not treat causation as a primitive, with no intrinsic relationship to correlation or necessity, but it must avoid the paradoxes that have resulted from attempts to reduce causality to statistical relations. 6. It should be compatible with indeterminism, and with merely probabilistic connections between cause and effect (chapters 5 and 6). 7. It should provide an account of the modularity (or locality) of causal reasoning: the role (recently much investigated by researchers in the field of artificial intelligence) of causation in enabling us to draw correct default conclusions in the presence of irrelevant information (appendix B). The last desideratum is especially important, since any theory of causation that does not account for the special virtues of causal reasoning is seriously incomplete. Researchers in logic and artificial intelligence, such as Judea Pearl (1988), have discovered that reference to causal relations plays an indispensable role in our commonsense reasoning about the world. The Yale Shooting Problem of McDermott and Doyle (which I discuss in appendix B) is an excellent example of the sort of problem of reasoning about prospective change that requires a causally informed description of the situation. I argue that the fundamental characteristic of causality that explains its importance in commonsense reasoning is the Markov property: when one fact is causally screened off from a second by one of its causes, then the conditional probability of the second on the cause is independent of the first fact. This justifies our exclusion of causally irrelevant information (information that is causally screened off from our prospective conclusions by our premises) in reasoning defeasibly.

1.5

The Ontology of Causation

In order to make sense of causal relations, we must be able to apply the partof relation (and the associated machinery of mereology) to the causal relata. This means that we must acknowledge the reality of concrete existences, tokens, that can play the role of concrete events and states (or "situations"). In addition to these situation-tokens, we will need abstract, repeatable situationtypes. The situation-types represent intrinsic qualities or characters of situationtokens. This choice of primitives is drawn from the work of Barwise, Perry, and Etchemendy (Stanford situation theory).

8

Realism Regained

The situation-tokens can serve as the truth-makers for propositions, playing the role that "facts" play in the philosophies of Austin, Bergmann, and Hochberg. When it is true that the cat is on the mat, there is a concrete cat-on-the-mat situation-token s that makes it true. This token s is of the cat-on-the-mat type. Complex situation-types can be constructed from simpler ones by means of logical operators, such as negation and disjunction. These operators should be interpreted by means of the strong Kleene three-valued truth tables or the four-valued Dunn tables (as explained in appendix A). In addition to tokens and types, there is a causal priority relation -