PH 201/400 – Week 1

1. PH 201/400 – Week 1 Scientific Realism and Antirealism

2. Approaching the Question Fact: Many scientific theories are ampliative – i.e. they go beyond what has been directly observed. What is the status of ampliative parts of science? Should we believe in them?

3. Example: Higgs Boson The so called “standard model” is our best theory of elementary particles. It postulates that there is a so called Higgs boson, which has roughly the following properties: Mass: ca 125 GeV Mean life span: ca 10−22 s Size: much smaller than subatomic particles.

4. Example: Higgs Boson (cont.) Question: it’s nice to have a good theory, but is there really such a particle?  go and look for it!

5. Example: Higgs Boson (cont.) 4th July 2012: The Higgs boson has been found

6. Examples: Higgs Boson (cont.)

7. Examples: Higgs Boson (cont.)

8. Example: Higgs Boson (cont.) The question, more precisely: Assuming the work in CERN has been done correctly and flawlessly, does the Higgs boson exist? Physicist at CERN have generated is an enormous amount of data, which have been processed with elaborate statistical techniques. At the end it is concluded that the particle exists.

9. Example: Higgs Boson (cont.) But no one has ever seen the particle. On the basis of the experimental evidence produced in CERN, should we believe that there really is a Higgs Boson? “Yes” Scientific Realism “No” Scientific Antirealism

10. 1. Getting Started Roughly speaking, one is a realist about x if one beliefs that x exists; one is an antirealist about x if one does not believe that x exists. Realism about what? Suggestions for x: The external world  metaphysical realism Universals  realism about properties Entities in scientific theories  scientific realism

11. Warning: often all these positions (and indeed others!) are univocally referred to as‘realism’. This is confusing. There is no such thing as unqualified realism, or realism per se. Always ask the question: realism about what? Realism about some x do not ipso facto commit you to realism about other xs.

12. Scientific Realism Introduced Ask the realism question about scientific entities. But why would any body do this? You may wonder: “of course genes and atoms exist, what are you going on about?!”

13. Scientific theories provide us with • good strategies when it comes to forecasting future events • a unified picture of reality, describing what things there are, how they are, and what laws they obey. But in doing so, scientific theories postulate a number of entities that are unobservable. Examples: the Higgs boson And: DNA, genes, viruses, microbes, fitness of organisms, atoms, electrons, quarks, super-strings, black holes, …

14. Terminology: The (putative!) entities posited by scientific theories are called theoretical entities. The terms that (putatively!) refer to such entities are called theoretical terms.

15. Question: Should we believe what science tells us beyond the appearances of things? Or more specifically, should we believe in the existence of theoretical entities? And should we believe that they behave as the theory says they do? The philosophical debate over scientific realism by and large revolves around these questions. The realist answer: yes!

16. Roughly speaking, scientific realism is the view that we should believe in what science tells us about reality, and in particular also in what it tells us about unobservables. Or a bit a more cautiously: scientific realism is “the view that mature and genuinely successful scientific theories should be accepted as nearly true.” (Psillos 1999, xvii)

17. Anti-realist: no! Roughly speaking, anti-realists understand scientific theories as instruments to predict observable phenomena or to systematise our knowledge; that is, as toolboxes, practical recipes or devices for the economy of thought. But as such theories do not reflect how reality behind the observable phenomena‘really is’. Other labels: instrumentalism.

18. 2. Scientific Realism Qualified Scientific realism involves the acceptance of four claims (0) Metaphysical realism There is a mind independent world. (Against idealism)

19. ‘Reality is prior to thought’ The world has a mind-independent structure. That is, when engaging in scientific investigation we do not project a certain structure (provided by our minds) onto the world; rather we discover features of the world that are there independently of any observer. Or to use a slogan that is popular with realists: we ‘carve nature at its joints’.

20. (2) Semantic realism Scientific theories have to be taken at face value. That is, scientific theories give us a literal descriptions of their subject matter and they can be true or false. In particular, theoretical terms refer. So if the theory is true, the entities postulated by the theory (or ones very similar to them) populate the world and the terms in our theories refer to them.

21. (3) ‘Epistemic optimism’ Mature and predictively successful scientific theories are (at least approximately) true of the world and we can know them to be so. That is, there is some kind of justification for the belief that certain theoretical assertions are true.

22. Antirealism then is the denial of one or several of these theses. • Deny (3): HumeanScepticism, Constructive Empiricism • Deny (2) and (3): Reductive Empiricism • Deny (1), (2), and (3): Constructivism • Deny (0), (1), (2), and (3): Idealism More about Antirealism next week.

23. 3. Arguing for Scientific Realism: ‘No Miracles Argument’ Intuition: The success of science calls for an explanation. Realism can provide such an explanation and instrumentalism can’t. Therefore realism is the right attitude toward theories. The ‘textbook version’ of the no miracles argument (NMA) is due to Putnam:

24. ‘The positive argument for [scientific] realism is that it is the only philosophy that does not make the success of science a miracle. That terms in mature scientific theories typically refer […], that theories accepted in mature science are typically true, that the same terms can refer to the same even when they occur in different theories – these statements are viewed not as necessary truths but as part of the only scientific explanation of the success of science, and hence as part of any adequate description of the science and its relations to its objects.’ (Putnam 1975, 73)

25. This argument can also be found, among others, in H. Poincaré, J.J.C. Smart, G. Maxwell, and R. Boyd, and S. Psillos, who developed different versions. But how exactly are we to understand this argument?

26. Inference to the best explanation Starting point: Naturalism The reasons for accepting a philosophical thesis – scientific realism in this case – are of the same kind as the reasons we give for accepting a scientific thesis: we appeal to its explanatory power, simplicity, strength, comprehensiveness, lack of ad hocness, and other theoretical virtues.

27. So what is this method? The realist’s answer: Inference to the best explanation (IBE) Other labels: ‘abduction, ‘the method of hypothesis’, ‘eliminative induction’, or ‘theoretical inference’.

28. ‘[…] one infers, from the fact that a certain hypothesis would explain the evidence, to the truth of that hypothesis. In general, there will be several hypotheses which might explain the evidence, so one must be able to reject all such alternative hypotheses before one is warranted in making the inference. Thus one infers, from the premise that a given hypothesis would provide a “better” explanation for the evidence than would any other hypothesis, to the conclusion that the given hypothesis is true.’ (Harman 1965, 89)

29. Examples: • ‘Where there is smoke there is fire.’ • Every day context: The light in Richard’s office is on and the keyboard is rattling … • Forensics: Smith is found dead in his flat with a shot wound inflicted by a Beretta 9mm. Jones’ DNA is found in the flat and Jones owns a Beretta 9mm … • Science: Does light consist of particles or is it a wave? Make an experiment:

31. The wave theory of light provides a good explanation for the observation; the particle theory doe not. Conclusion: the wave theory is true by IBE.

32. In general: • From theory T we obtain the hypothesis that phenomenon X obtains. • Evidence: X does obtain. • No theory better explains why X obtains than T does. • Conclusion (by IBE): theory T is true.

33. Next crucial step: • Use IBE to justify scientific realism. • Starting point: • X science is successful • T  scientific realism. Reasoning: Realism suggests that mature scientific theories have to be successful and it affords us better explanation for why this is so than any other philosophical position.

34. Therefore, by IBE: realism is true. • Questions: • Is the use of IBE in this context justified? • Doesn’t the argument presupposes what it is supposed to prove, namely that IBE is a reliable inferential pattern?