Markku Roinila Leibniz on Rational Decision-Making Philosophical Studies from the University of Helsinki 16 Filosofisia tutkimuksia Helsingin yliopistosta Filosofiska studier från Helsingfors universitet Philosophical studies from the University of Helsinki Publishers: Department of Philosophy Department of Social and Moral Philosophy P. O. Box 9 (Siltavuorenpenger 20 A) 00014 University of Helsinki Finland Editors: Marjaana Kopperi Panu Raatikainen Petri Ylikoski Bernt Österman ISBN 978-952-92-1992-6 (paperback) ISBN 978-952-10-3896-9 (PDF) ISSN 1458-8331 Vantaa 2007 Dark Oy Leibniz on Rational Decision-Making Markku Roinila Abstract In this study I discuss G. W. Leibniz's (1646-1716) views on rational decision-making from the standpoint of both God and man. The Divine decision takes place within creation, as God freely chooses the best from an infinite number of possible worlds. While God's choice is based on absolutely certain knowledge, human decisions on practical matters are mostly based on uncertain knowledge. However, in many respects they could be regarded as analogous in more complicated situations. In addition to giving an overview of the divine decision-making and discussing critically the criteria God favours in his choice, I provide an account of Leibniz's views on human deliberation, which includes some new ideas. One of these concerns is the importance of estimating probabilities – in making decisions one estimates both the goodness of the act itself and its consequences as far as the desired good is concerned. Another idea is related to the plurality of goods in complicated decisions and the competition this may provoke. Thirdly, heuristic models are used to sketch situations under deliberation in order to help in making the decision. Combining the views of Marcelo Dascal, Jaakko Hintikka and Simo Knuuttila, I argue that Leibniz applied two kinds of models of rational decision-making to practical controversies, often without explicating the details. The more simple, traditional pair of scales model is best suited to cases in which one has to decide for or against some option, or to distribute goods among parties and strive for a compromise. What may be of more help in more complicated deliberations is the novel vectorial model, which is an instance of the general mathematical doctrine of the calculus of variations. To illustrate this distinction, I discuss some cases in which he apparently applied these models in different kinds of situation. These examples support the view that the models had a systematic value in his theory of practical rationality. Contents ACKNOWLEDGEMENTS ............................................................. 9 INTRODUCTION............................................................................ 11 PART I: DIVINE CHOICE 1. God's Rational Choice ............................................................... 19 2. Models of Creation.................................................................... 28 2. 1. Nicholas Rescher's Trade-Off View..................................... 31 2.1.1. Optimums and Calculus of Variations...................... 36 2. 2. David Blumenfeld's Maximum View................................... 41 2. 3. Donald Rutherford's Maximum View.................................. 43 2. 4. Optimum or Maximum? ...................................................... 46 2. 4. 1. Does simplicity produce variety?............................... 47 2. 4. 2. Architectonics and the Principle of Optimal Order in Tentamen Anagogium ................................................ 52 2. 4. 3. The Tiling Problem in De rerum originatione radicali 64 2. 5. Moral Goodness in God's Choice.......................................... 69 2. 5. 1. Optimising and Moral Goodness............................... 74 2. 5. 2. Happiness in the Actual world ....................................... 79 3. A Summary of Part I ................................................................ 84 PART II: HUMAN COGNITION, REASONING AND THE THEORY OF PROBABILITY 4. Human Reasoning and Cognition ............................................ 87 4. 1. Truths of Reason vs. Truths of Fact.................................... 88 4. 2. Innate Ideas......................................................................... 93 4. 3. The Theory of Cognition ..................................................... 95 4. 3. 1. The Theory of Cognition in Meditationes de cognitione, veritate et ideis......................................................... 96 4. 3. 2. Minute Perceptions .................................................... 100 4. 3. 3. Apperception, Attention, Memory and Imagination............................................................................. 105 4. 3. 4. Moral Identity and the Problem of Apperception in Animals ............................................................................... 116 5. An Analysis of Contingent Truths ........................................... 122 6. The Theory of Probability.......................................................... 133 6.1. The Classic Probability Theory ............................................ 135 6. 2. Leibniz's Views on Probability ........................................... 142 6. 2. 1. Calculating Probability............................................. 145 6. 2. 2. Estimating Probability............................................... 150 6. 2. 2. 1. Proofs and Presumptions .................................... 154 6. 2. 2. 2. Some Examples..................................................... 156 7. Summary of Part II................................................................... 158 PART III: HUMAN RATIONAL DECISION-MAKING 8. Practical Reason and Human Action........................................ 161 9. Leibniz's Moral Philosophy ...................................................... 164 9. 1. Goodness, Love, Justice and Pleasure ........................... 167 9. 2. Happiness and Virtue...................................................... 179 10. Deliberation ............................................................................ 187 10. 1. Some Major Influences of Leibniz's Views ....................... 187 10. 2. Leibniz's Views on Deliberation ....................................... 193 10. 2. 1. The Deliberation in the Soul ................................... 200 10. 2. 2. The Passions and Deliberation ............................... 208 10. 2. 3. Weakness of the Will ................................................... 213 11. Models of Decision-Making.................................................... 229 11. 1. Moral Calculus ................................................................. 229 11. 2. The Pair of Scales Model................................................... 232 11. 2. 1. An Example of Balancing For or Against.............. 237 11. 2. 2. Examples on Compromises Achieved by Finding a Balance ................................................................... 240 11. 3. Complicated Decisions...................................................... 248 11. 3. 1. The Vectorial Model of Rational Decision-Making 249 11. 3. 2. More Examples of the Use of the Vectorial Model 262 11. 3. 2. 1. Centres of Gravity ................................................ 262 11. 3. 2. 2. Doctrina conditionum............................................. 264 11. 3. 2. 3. Religious Controversies....................................... 266 11. 3. 2. 4. Political Controversies........................................ 275 12. Summary of Part III................................................................ 278 GENERAL SUMMARY................................................................... 281 ABBREVIATIONS ........................................................................... 287 BIBLIOGRAPHY ..................................................................... 289 Acknowledgements Writing this study has been a long and multi-phased process and there are many people who deserve my gratitude. First, I would like to thank my supervisor, Professor Lilli Alanen, who has been a kind, yet critical witness of my struggle to express Leibniz's complicated views. No less important has been Academy Professor Simo Knuuttila, who suggested the topic and has since read and commented in depth on the numerous drafts of this work. My pre- examiners, Professors Donald Rutherford (University of California), Olli Koistinen (University of Turku) and Mikko Yrjönsuuri (University of Jyväskylä), gave me considerable help in formulating my views, for which I am most grateful. My thanks are also due to Joan Nordlund M. A. who has put my English into an understandable form. There are a number of other people who have commented on or discussed various parts of my study, or have helped me in other ways. Thus I thank Professor Herbert Breger (Leibniz-Archiv, Hanover), Professor Marcelo Dascal (University of Tel Aviv), Professor Harmut Rudolph (Leibniz-Arbeitsstelle, Potsdam), Professor Jyrki Siukonen (Academy of Fine Arts, Helsinki), Dr. Andreas Blank (The Cohn Institute for the History of Science and Ideas, University of Tel Aviv), Dr. Arto Repo (University of Turku), and Doktorand Peter Myrdal (University of Uppsala). My work with this thesis has benefited from my involvement in various official and non-official circles. First, I have had the privilege of working at the Department of Philosophy at the University of Helsinki, which has provided a safe haven for me in my labour. My colleagues at the History of Mind Research Unit of the Finnish Academy