1 How to be a scientific realist (if at all): A study of partial realism Dean Peters A thesis submitted to the Department of Philosophy, Logic and Scientific Method of the London School of Economics for the degree of Doctor of Philosophy, London, October 2012 2 Declaration I certify that the thesis I have presented for examination for the MPhil/PhD degree of the London School of Economics and Political Science is solely my own. The copyright of this thesis rests with the author. Quotation from it is permitted, provided that full acknowledgement is made. This thesis may not be reproduced without my prior written consent. I warrant that this authorisation does not, to the best of my belief, infringe the rights of any third party. I declare that my thesis consists of 86,011 words, including footnotes but excluding references. Dean Peters 3 Abstract "Partial realism" is a common position in the contemporary philosophy of science literature. It states that the "essential" elements of empirically successful scientific theories accurately represent corresponding features the world. This thesis makes several novel contributions related to this position. Firstly, it offers a new definition of the concept of “empirical success”, representing a principled merger between the use-novelty and unification accounts. Secondly, it provides a comparative critical analysis of various accounts of which elements are “essential” to the success of a theory, including structural realism and the divide et impera strategy. A novel account of essentialness, entitled the “empirically successful sub-theory account”, is defended. Thirdly, it is argued that the realism/anti-realism debate should put to the side metaphysical questions and focus instead on partial realism’s commitment to the continuity of science. Because this commitment lacks metaphysical implications, it is referred to as “deflationary realism”. Anti-realists cannot reject deflationary realism as a matter of a priori principle; its overall viability (and therefore that of partial realism) can therefore only be assessed by a careful examination of the history of science. Finally, another consequence of partial realism, named "partial rationalism", is defended. Partial rationalism states that, in cases where several competing theories have been suggested, scientists are rational just in case they accept the essential elements of each of the scientific theories on offer. This novel position subverts the existing literature on scientific “revolutions”, as it sometimes demands that scientists devise a synthesis between competing scientific theories, instead of “choosing” only one. The philosophical points defended in this thesis are illustrated and supported by case studies from the history of science, including Fresnel’s wave theory of light, the Copernican revolution, the “neo-Darwinian synthesis” in evolutionary biology, the “prion revolution” in molecular biology, the miasma theory of disease, and the chemical revolution 4 Outline of thesis Acknowledgements ......................................................................................................... 7 Thesis overview ............................................................................................................ 10 Chapter 1. Naive realism, partial realism and deflationary realism .......................... 14 Chapter 2. Empirical success and theory confirmation ............................................ 69 Chapter 3. What parts of scientific theories are “essential”? .................................. 128 Chapter 4. Rationality and theory choice ............................................................... 196 Chapter 5. Problem cases ..................................................................................... 225 Thesis summary .......................................................................................................... 256 References.................................................................................................................. 261 5 Table of Contents Acknowledgements .............................................................................................. 7 Thesis overview .................................................................................................. 10 Chapter 1. Naive realism, partial realism and deflationary realism ................ 14 1. Chapter overview ...................................................................................... 14 2. Scientific realism and the no-miracles argument ...................................... 15 3. Critical analysis of the NMA ...................................................................... 22 4. Naive realism and the pessimistic meta-induction .................................... 34 5. Partial realism and deflationary realism .................................................... 41 6. What elements are preserved? ................................................................. 45 7. The optimistic induction ............................................................................ 49 8. Deflationary realism and constructive empiricisim .................................... 56 9. The argument from continuity to truth ....................................................... 59 10. Chapter summary ..................................................................................... 66 Chapter 2. Empirical success and theory confirmation .................................. 69 1. Chapter overview ...................................................................................... 69 2. Predictivism .............................................................................................. 70 3. Temporal novelty ...................................................................................... 72 4. Theoretical novelty .................................................................................... 78 5. Use-novelty ............................................................................................... 82 6. Severe testing ........................................................................................... 86 7. Weak predictivism ..................................................................................... 94 8. The unification view ................................................................................ 103 9. Theoretical unity and theoretical simplicity .............................................. 109 10. Deductive entailment and confirmation ................................................... 120 11. Chapter summary ................................................................................... 125 Chapter 3. What parts of scientific theories are “essential”? ....................... 128 1. Chapter overview .................................................................................... 128 2. Direct reference approaches ................................................................... 129 3. Retrospective versus prospective accounts of essentialness ................. 134 4. Entity realism and phenomenological realism ......................................... 143 5. Structural realism .................................................................................... 152 6. Semi-realism ........................................................................................... 162 7. Working posits ........................................................................................ 165 6 8. Differing interpretations of the working posits idea ................................. 169 9. Essentially contributing parts of derivation internal posits ....................... 177 10. The empirically successful sub-theory approach .................................... 184 11. Chapter summary .................................................................................. 192 Chapter 4. Rationality and theory choice ..................................................... 196 1. Chapter overview .................................................................................... 196 2. Rationality and theory choice .................................................................. 197 3. Partial rationalism ................................................................................... 204 4. The Copernican revolution ...................................................................... 210 5. The neo-Darwinian synthesis .................................................................. 216 6. The prion revolution ................................................................................ 219 7. Chapter summary ................................................................................... 223 Chapter 5. Problem cases ........................................................................... 225 1. Chapter overview .................................................................................... 225 2. Putative counterexamples to realism ...................................................... 226 3. The miasma theory of disease and the contagionist revolution .............. 230 4. Assessing the miasma theory ................................................................. 240 5. The phlogistion theory and the chemical revolution ................................ 242 6. Assessing the chemical revolution .......................................................... 247 7. Chapter summary ................................................................................... 254 Thesis summary ..............................................................................................