1 Realism vs Anti-realism

2 Topics The Problem of Unobservability The “No Miracles” Argument The Observable / Unobservable Distinction The Underdetermination Argument for Antirealism

3 The Problem of Unobservability Observable ordinary objects Unobservable theoretical objects –Note: theoretical  unobservable, e.g. “mass”, “element”. ~ m Very tiny tiny... tiny superstrings!

4 Questions: –Do unobservable theoretical entities really exist and are their descriptions true? –Is theoretical knowledge about unobservables possible? (Cf. also the Problem of Induction) –Are unobservable theoretical constructs merely instruments for making observable predictions without ontological import? E.g. “center of mass” does not refer to any physical objects, but a spatial point only.

5 Realist & anti-realist interpretations of the kinetic theory of gases: –It can correctly predict various observable behaviour of gases, e.g. Boyle’s Law.

6 Realism –The aim of science is to provide a true description of both the observable and unobservable part of reality –This aim is attainable.

7 Antirealism (or Instrumentalism): –The aim of science is to provide a true description of the observable part of the world only. –For the unobservable part, only agnosticism is possible. –Unobservable theoretical constructs are for us merely instruments for making observable predictions.

8 Copernicus’s theory was originally interpreted antirealistically by Osiander who wrote the Preface for Copernicus’s main work, On the Revolutions of the Heavenly Bodies: –“... it is the duty of an astronomer to compose the history of the celestial motions through careful and skillful observation. Then turning to the causes of these motions or hypotheses about them, he must conceive and devise, since he cannot in any way

9 –attain to the true causes, such hypotheses as, being assumed, enable the motions to be calculated correctly from the principles of geometry, for the future as well as the past. The present author [Copernicus] has performed both these duties excellently. For the hypotheses need not be true nor even probable; if they provide a calculus consistent with observation that alone is sufficient.”

10 The “No Miracles” Argument “The positive argument for realism is that it is the only philosophy that doesn’t make the success of science a miracle” – H. Putnam The statue was claimed to sweat. Would you believe in it if there’s a non- miraculous explanation?

11 Main points of the argument: –What explains the theory’s close fit with the observational data? –Being an antirealist is akin to believing in miracles. –So, realism is more plausible.

12 One historical reason for accepting the atomic thesis in the early 20 th century: –Convergence on Avogadro's number under measurements in such diverse phenomena as Brownian motion, alpha decay, x-ray diffraction, electrolysis, blackbody radiation, and so on. –What is the best explanation? Ref.:

13 It is an inference to the best explanation (IBE): –X: Convergence on Avogadro's number –A: The atomic thesis –P 1 : A explains X better than its rivals, B, C, and so on. P 2 : The ability of a hypothesis to explain something better than all its rivals is a mark of its truth. C: Hence, A is true. A sort of reasoning commonly used in daily life, e.g. Sherlock Holmes – –“The Science of Deduction”

14 Empirical Success Truth

15 One anti-realist response: –Counterexamples from the history of science –E.g. the phlogiston theory of combustion: Widely accepted until the end of the 18th century + Substance ResiduePhlogiston

16 Realist refined argument: –By appealing to “approximate truth” rather than “exact truth”. Must empirical success lead to approximate truth?

17 Counterexample from the history of optics – drastic changes of the conception of light: –Newton’s ( ) theory: Light as beams of material corpuscles –Fresnel’s ( ) theory: Light as transverse wave in an all- pervasive elastic medium - ether

18 –(Modified) Maxwell’s ( ) theory: Light as fluctuating electric and magnetic fields-in-themselves without medium –Einstein’s ( ) theory: Light as quanta, the photons

19 These theories were empirically successful and had made progress, but did they move closer and closer to the truth? What is light? –Material particles –Waves in an elastic medium, ether –Fluctuating fields-in-themselves –Photons –Next ???

20 Also, it seems difficult to regard, say, Fresnel's theory as approximately true, since ether - a basic entity in the theory - is now believed not to exist. Would you think that this picture gives you an approximately true depiction of the environment if in fact there was no fog there?

21 Paper topics? –What is approximate truth? –What notion(s) of approximate truth is(are) relevant to this dispute? How?

22 The moral drawn by the antirealist: –Modern scientific theories should not be taken as even approximately true, just because they are so empirically successful. But one may suggest: –An empirically successful theory is probably on the right line. Which interpretation of probability is involved? –Frequency, subjective, logical, and so on. Would this sense of probability help solve the problem?

23 Some Positions in the Debate An influential form of antirealism: –Van Fraassen’s constructive empiricism Weaker forms of realism: –Convergent realism –Karl Popper’s conjectural realism –Ian Hacking’s & Nancy Cartwright’s Entity Realism Attempts to capture the best of both worlds: –A. F. Chalmers’s unrepresentative realism –John Worrall’s structural realism

24 claims about unobservables are: truefalsecan’t tell interpreted literally realism [ fundamentalism ] fictionalism [atheism] constructive empiricism [agnosticism] interpreted nonliterally positivism [liberal theology] An Analogy to Positions in Theology