The final frontier: Inference to the Best Explanation (IBE)

1. The final frontier: Inference to the Best Explanation (IBE) “[The] primary issue in the defence of scientific realism is selective scepticism: epistemic discrimination against unobservables; unobservable rights” Michael Devitt (220)

2. Constructive Empiricist: the explanatory power of a theory is pragmatic and not because the answer is compelled by the way the world is. The realist, of course, claims the opposite. Successful theories explain because they are true or almost true. Their argument against constructive empiricism rests on the use of Inference to the best explanation in cases of unobservables. Constructive Empiricism vs. Realism on explanations

3. An example • Consider the following example from chemistry. • Realists would say that given all the data we have about chemical reactions and our ability to build instruments to manipulate them, the molecular account is literally true; that there are different chemical atoms. • Not only can the theory of molecules make correct predictions, but it does explain the phenomena. • Hydrochloric acid is HCl and ethanol is C2H5OH, and there are hydrogen, oxygen and chlorine atoms.

4. Consider the following example using observables: There is a constant running sound behind the walls Bags containing food have been clawed open There are mice behind the wall Contrast the previous example with the following argument using unobservables: 1) Tracks in a cloud chamber 2) Electrical phenomena (i.e. electricity works!) 3) There are electrons. Constructive Empiricism on IBE reasoning

5. What would be the realist’s position? The realist would say that it is true that the mice and electrons exist. What would van Fraassen say about these two examples? van Fraassen might say that mice (observable) exist, but not electrons (unobservable) Constructive Empiricism on IBE reasoning

6. Scientific realism and inference to the best explanation • Realists would say IBE works for both the realm of observables and unobservables because “the positive argument for realism is that it is the only philosophy that doesn’t make the success of science a miracle” (Putnam cited on p. 213). • Why ‘no miracles’?

7. ‘No miracles’ • Consider biology. Not only do we have a theory involving cells, but we have also built instruments—microscopes, electron microscopes, etc—with which to intervene successfully at the cellular level. It would be a case of “cosmic coincidence” for all those theories—cells, optics, electromagnetism—to work at the same time.

8. Constructive Empiricist’s response to the ‘no miracles’ argument • How might van Frassen respond? • Coincidences can be explained. • van Frassen: “It was by coincidence that I met my friend in the market—but I can explain why I was there, and he can explain why he came, so together, we can explain how this meeting happened. We call it a coincidence, not because the occurrence was inexplicable but because we did not severally go to the market in order to meet” (216) • Is this answer satisfactory?

9. Constructive Empiricist’s response to the ‘no miracles’ argument • Van Frassen’s response misses the point of the realist argument—the repeated success of scientific theories cannot be explained in terms of the kind of coincidence cited in van Frassen’s response.

10. Another Constructive Empiricist response to the ‘no miracles’ argument • Remember the constructive empiricist cite pragmatic reasons for solving underdetermination: Their aim is only for empirical adequacy at the observable realm. • So, constructive empiricists can claim that we have from the history of science pragmatic grounds for believing that the theories—cells, optics, electromagnetism, etc.—will continue to be empirically adequate

11. The realist counter-argument on ‘no miracles’ • The realist could point out that the argument from pragmatic grounds is compatible with their own. • Consider the distinction between phenotype and genotype. • The constructive empiricist offers a phenotypic argument (surface explanation) for why certain theories have survived, but that is compatible with a genotypic argument (deep features) of why those theories are successful. • Here think about a phenotypic and genotypic explanation for why giraffes have long necks

12. Phenotypic, genotypic, … • How would the constructive empiricist respond to the realist attempt to co-opt them? • They will not be swayed by the realist attempt because one of the tenets of their anti-realism is to avoid explanations that appeal to ‘deep’ structures (i.e. unobservable).

13. van Frassen’s criticisms of IBE • van Frassen has two criticisms against IBE: • The argument from indifference: given a set of empirically equivalent but ontologically incompatible theories to choose from, it is highly improbable that the true theory is in that set. So it is highly improbable that the best explanation is true. • The argument from the best of a bad lot: Given the first argument, the best explanatory hypothesis may just be the best of a set of false theories. How do we know that other hypotheses not being considered are not as good or better than what we have?

14. The realist’s response • First, the set of candidates is not arbitrary. Theory choice includes background knowledge which narrows the possible candidates of hypotheses. It is explanatory considerations of the candidates that determine the best hypotheses. • Furthermore, the same problem applies to the constructive empiricist. How do they know that the best empirically adequate theory is included in the set of candidates?

15. The realist strikes back: selective scepticism • Furthermore, the realist can point to a problem for the constructive empiricist: What is the reason for claiming that realm of observables is immune to the problem of underdetermination? • If the constructive empiricist (i.e. van Fraassen) says mice exist but electrons do not, then she is inconsistent in rejecting realists’ claims, using IBE, about unobservables.

16. Constructive empiricism and Inference to the best explanation • The realist argues that the constructive empiricist cannot make the claims they do about observables. • Remember for van Frassen, dinosaurs are observables, even though they are not observed. • But hypothesis about unobserved objects and events are just as susceptible to the problem of underdetermination as theories about unobservable objects and events • Why?

17. The underdetermination argument • Consider the hypothesis that a meteor struck Io, one of the moons of Jupiter, in 2001. • The astronomer could point to satellite pictures of Io before 2001 which does not show the crater. • But is that the only explanation? • How about geothermal activity on Io? What about problems with the camera? • How do we solve the problem of underdetermination in this case?

18. The underdetermination argument • The point of the realist’s argument is that if the underdetermination argument is applied consistently, then we can only have knowledge of things that have been observed! • Wouldn’t the result be that most of what passes for knowledge in the sciences isn’t knowledge at all, since they concern objects and events that haven’t been observed? • The constructive empiricist needs to give us a principle for allowing her to make the claims she does about those observables which are not observed which does not apply to unobservables (i.e. theoretical entities).

19. The underdetermination argument • The issue here is that for realists, if a particular explanation is agreed to be the best explanation of the phenomena in question, it is irrational not to adopt it because the best explanation is linked to truth. • van Frassen on the other hand is presenting constructive empiricism not as a theory that one must adopt if one were rational, but rather as an epistemic position that may be adopted which accounts for all that we need to know about science.

20. The Constructive Empiricist’s response • van Frassen likens his position to a particular conception of rationality. • He contrasts the Prussian and the English points of view: • Prussian: forbids that which is not specifically allowed. • English: allows anything that is not specifically forbidden. • van Frassen likens his position (which he calls voluntarism) to the English point of view: “what is rational to believe includes anything that one is not rationally compelled to disbelieve” (223)

21. Constructive empiricism and inference to the best explanation • He claims “IBE may be indispensable in acquiring reasonable expectations and thus may be pragmatically indispensable” (223). • For the constructive empiricist, IBE is acceptable as a practice of inference for empirical adequacy, NOT because it is a rule of reasoning which leads to truth. • Remember what Hume said about our use of induction.

22. Constructive Empiricism and inference to the best explanation • For van Frassen, IBE does not compel us to be scientific realists. • The realist claims that van Frassen’s denial of IBE for unobservables is arbitrary • van Frassen argues that to insist, as the realists do, to go beyond the empirical adequacy of theories to account for the nature of science, we are taking unnecessary risks (i.e. making claims about unobservables) for no extra empirical gain.

23. Constructive Empiricism and inference to the best explanation • What is the extra bit that scientific realism gives from an empiricist point of view? • ‘The way the world is’ but that’s just more metaphysics. van Frassen’s rejection of realism rests on his empiricism (in Constructive empiricism): “empiricists should repudiate beliefs that go beyond what we can (possibly) confront with experience, and this restraint allows them to say ‘good bye to metaphysics’” (225).

24. The final word • The realist counters that van Fraassen’s position commits him to skepticism not only of the unobservable realm, but also the realm of commonsense realism (the observables) if underdetermination were applied consistently. • van Fraassen’s response: Just as the success of science needs no metaphysical explanation, the realm of common sense, the everyday world, needs no metaphysical explanation. • The everyday world is a brute fact. We do not need to infer or argue for its existence.

25. One final challenge • The realist on the other hand is susceptible to a challenge themselves with regards to IBE. The challenge is as follows: “since it is IBE involving unobservables that is in question in the realism debate, it is circular to appeal to the explanatory power of scientific realism at the meta-level [i.e. using IBE again] to account for the overall success of science” (218) • How might the realist respond?

26. One final challenge • Recall the discussion earlier with the problem of induction (section 2.2.8): can there be any non-circular justification of inductive and deductive reasoning? • What other position is available to us?