VIEWS: 1 PAGES: 24 POSTED ON: 6/24/2012
Resisting the Pessimistic Induction Kareem Khalifa Department of Philosophy Middlebury College Overview No Miracles versus Pessimistic Induction Carving up Laudan’s Hit List Genuine versus spurious empirical success Psillos’s Divide et Impera Explaining genuinely empirically successful, but non- referring theories Theoretical constituents Essential contributions Objections to Psillos No Miracles Argument Scientific theories are empirically successful. The approximate truth of these theories best explains their empirical success. So scientific theories are approximately true. The Pessimistic Induction attacks the 2nd premise. Pessimistic Induction If a theory’s approximate truth best explains its empirical success, then there should be few/no empirically successful but false theories. But there are! Recall the Hit List! …or see the next slide… So a theory’s approximate truth need not be the best explanation of its empirical success. The Hit List The crystalline spheres of ancient and medieval astronomy The humoral theory of medicine The effluvial theory of static electricity ‘Catastrophist’ geology, including the Noah’s Flood The phlogiston theory of chemistry The caloric theory of heat The vibratory theory of heat The vital force theories of physiology The electromagnetic aether The optical aether The theory of circular inertia Theories of spontaneous generation Important Details in the Pessimistic Induction (S307) A. Current successful theories are approximately true. B. If current successful theories are truthlike, then past theories cannot be. Ex. If the oxygen theory is truthlike, then phlogiston is not. C. These characteristically false theories were, nonetheless, empirically successful. Thus, a theory’s approximate truth need not be the best explanation of its empirical success. I use the DIVIDE et IMPERA MOVE to get rid of the rest by Psillos vs. the Pessimistic Induction showing how their genuine empirical success depended on B. If current the extent to which they successful theories anticipated the current theory. are truthlike, then past theories cannot be. C. These characteristically false theories were, Many realists whittle down this nonetheless, list by restricting it to theories empirically with genuine empirical successful. successes… Whittling down the Hit List (S307) “Any theoretical framework can be made to fit the phenomena-and hence to be 'successful'-by simply writing the right kind of empirical consequences into it.” That shouldn’t count as genuine empirical success though! Genuine empirical success = novel predictions. This takes care of most members of the hit list, since they are not genuinely empirically successful in the sense of yielding novel predictions. But… There are some false theories that yielded novel predictions, and thus were genuinely empirically successful. Fresnel's theory of diffraction novelly predicted that if an opaque disk intercepts the rays emitted by a light source, a bright spot will appear at the center of its shadow A brief digression on Fresnel Fresnel believed that light travels as a wave through the luminiferous ether From this, he made the novel prediction that if light hit an opaque disk, the disk will cast a shadow with a very bright center But we now know that there is no ether, and that light behaves like both a wave and a particle… So this would seem to suggest that novel predictive theories need not be approximately true… Enter… The strategy Take a past theory that made successful novel predictions DIVIDE its theoretical/unobservable entities into: Essentially contributing theoretical constituents; and Idle theoretical constituents. CONQUER the novel prediction by showing that they are the result of essentially contributing theoretical constituents, and the latter have been retained in our current theories. More on dividing A theoretical constituent is a particular law or mechanism posited by a theory, but not the whole theory A theoretical constituent H essentially contributes to a novel prediction P if: H together with another set of hypotheses H' (and some auxiliaries A) entail P; H' and A alone cannot yield P; and No other available hypothesis H* which is consistent with H' and A can replace H without loss in the relevant derivation of P. Otherwise, H is idle. Fresnel Again Most of the properties attributed to ether were idle with respect to Fresnel’s novel prediction The essentially contributing constituent was Lagrangian dynamics, which is still used in contemporary physics We now attribute Lagrangian properties to electromagnetic fields rather than ether. So the novel empirical success of ether theories is best explained by Lagrangian dynamics So Lagrangian dynamics is approximately true. Objections to Psillos: Overview Must current theories be true? Where have all the good theories gone? Are essential contributions really essential? Are realists good historians of science? Objection 1: Must current theories theories be true? Recall Psillos’s characterization of the Pessimistic Induction: A. Current successful theories are approximately true. B. If current successful theories are truthlike, then past theories cannot be. C. These characteristically false theories were, nonetheless, empirically successful. However, the antirealist needs something much weaker than A, i.e., If any theories are truthlike, our current successful theories are it. Implications of this for the Pessimistic Induction If any theories are truthlike, our current successful theories are it. Thus, even if divide et impera is otherwise flawless, we would only be entitled to the following: • If our current theories are truthlike, then our past theories had truthlike theoretical constituents. But we still haven’t proven that our current theories are truthlike. Objection 2: Where have all the good theories gone? To whittle down the Hit List, realists make the criterion of empirical success more stringent, e.g., using novel predictions. However, the more stringent the criterion, the greater the number of irrational/unsuccessful scientific theories. Thus, if novel prediction is the mark of genuine empirical success, then even realists should accept theories that are technologically, observationally, retrodictively, and/or explanatorily successful can be false with no penalty. But that’s most theories! Look at the Hit List! So we can be antirealists about most theories.` Objection 2 continued Furthermore, why is it that only theories yielding novel predictions require realist explanations of their success? If it’s merely to “stump the antirealist,” then this looks ad hoc. Objection 3: Are essentially contributing constituents essential? Recall: A theoretical constituent H essentially Underdetermination: We contributes to a novel could have a different set of prediction P if: hypotheses and auxiliaries H together with another that would yield P! set of hypotheses H' (and some auxiliaries A) entail P; H' and A alone cannot yield P; and This could just speak to our No other available lack of imagination. The fact hypothesis H* which is that H* is unavailable consistent with H' and A can replace H without loss doesn’t mean it’s false, in the relevant derivation which is what realism of P. requires. Objection 4: Are realists good historians of science? The realist claims that a novel prediction happened because a past theory used the same theoretical constituents that current theories use. However, “with hindsight, we can rather easily work it out so that the theoretical constituents that 'contributed' to the successes of past theories turn out to be those which were, as it happens, retained in subsequent theories” (S311) Psillos’s Reply to Objection 4 With their own current theories, scientists take different attitudes towards whether something is essential or merely speculative/tentative. So realists can do this too. It is possible to identify essential contributors without the benefit of hindsight. Rebuttal to Psillos But even very good scientists aren’t great at this. Look at Maxwell on the status of ether: Whenever energy is transmitted from one body to another in time, there must be a medium or substance in which energy exists after it leaves one body and before it reaches the other. In effect, this just produces another pessimistic induction over the course of scientists’ judgments about what is an essentially contributing theoretical constituent. Recap The Pessimistic Induction can be challenged on the grounds that: Many members on Laudan’s Hit List are not genuinely empirically successful. Divide et Impera: The ones that are can be explained by their having truthlike theoretical constituents. There are at least four objections to these challenges to the Pessimistic Induction.
Pages to are hidden for
"Resisting the Pessimistic Induction"Please download to view full document