Prueba de hipótesis específica 4

Some philosophers suggest that a scientific explanation consists in a theory’s describing a variety of apparently diverse and independent types of phenomena using the same small set of terms. This enables many apparently independent types to be reduced in number. By unifying these types of phenomena, the theory thereby explains them (Friedman 1981).

For example, prior to Newtonian mechanics, the behaviour of planets, tides, terrestrial projectiles and celestial bodies seemed to be independent types of phenomena, each requiring their own explanation (if they had an explanation at all). Newtonian mechanics describes the behaviour of each of these types in terms of their masses, velocities and the gravitational forces acting on them. Newtonian mechanics unified what had otherwise seemed to be a heterogeneous collection of types of thing. By achieving this unification, Newton’s theory reduced the number of independent types of thing, and it thereby explained the behaviour of things of each type in the collection.

3 See Oddie (1982) and Colyvan (2001, ch. 3) for further discussion.

Despite the intuitive appeal of this view of scientific explanation, it has proved hard to make precise the crucial notion of “independent type of phenomena.” Moreover, the closeness of the connection between unifica-tion and explanaunifica-tion is open to quesunifica-tion (Barnes 1992, Humphreys 1993).

Bearing these reservations in mind, let’s consider whether philosophy can emulate this practice of explanation by unification. Various philosophers have seen themselves as explaining phenomena by unifying them. It seems that Plato did so (Cherniss 1936). More recently, Swoyer sees theo-ries of properties as offering “unified and integrated accounts” of certain mathematical, semantic and scientific phenomena (Swoyer 1999, 126). We saw in chapter 4, §5 that David Lewis claims that there exists a plurality of possible worlds, where a possible world is a thing of the same type as the actual world. Lewis seeks to explain the content of sentences, and much else besides, in terms of possible worlds (Lewis 1986, ch. 1). Part of his case for his theory of modal realism is the theoretical unification that he thinks that it achieves (Lewis 1986, 3–5). Modal realism has even been described as “offering the best account of the nature of science and of the world” (Bigelow and Pargetter 1990, 345).

The explanatory credentials of Lewis’s theory, however, have been challenged. Michael Friedman has levelled the following objection (Friedman 1981, 13-14, his italics):

It must be possible to show how creatures like us acquire and employ a language with the properties that the semantic the-ory ascribes to it. It must be possible to show how the theo-retical structures assumed in the semantic theory play a role in the actual process of language acquisition and use…. But in possible-worlds semantics the postulated semantic structure appears to be totally divorced from the psychological proc-ess of language acquisition and use. How do we, as finite crea-tures in this world, relate to entities (and sets of entities, and sets of sets of entities …) in other possible worlds? If anything, possible-world semantics makes it harder to connect linguistic theory with psychological and social theory than it was before.

Possible-worlds semantics appears to lead away from, rather than toward, theoretical unification.

Friedman’s objection is not that Lewisian possible worlds do not caus-ally act on objects in the actual world. The objection concerns the puzzle of how what is the case at other possible worlds could be explanatorily relevant to what occurs at the actual world — for example, in our actual

learning and use of language. Consequently, Friedman alleges that Lewis’s theory disunifies our semantic and psychological theories.⁴

A more general worry about philosophical appeals to unification as explanation is that whereas every unification is a re-description of certain phenomena, not every re-description is a unification, and some re-descriptions may masquerade as unifications and not be genuinely explanatory (Kraut 2001, 155–56). Astrology says that every event that is fated has to happen, and it re-describes every event of every type as a fated event. Astrology is thereby a comprehensive theory, but it is a poor potential explanation of any event. So, if we preserve the link between unification and explanation, astrology is not a unifying theory.

The main reason why astrology is a poor potential explanation is that it has no predictive power whatever. In addition, it has no explanation of how the supposed causes (the movements of the stars) can produce the effects they are said to explain. Moreover, according to the scientific theories that we currently accept the distribution of planets and stars at a time has no explanatory relevance to the occurrence of (say) storms or lottery results. Proponents of modal realism claim that positing possible worlds offers a comprehensive way of describing different phenomena.

But is it a good explanation of them? As noted, Friedman cannot see the relevance of the distribution of possible worlds to our acquisition or use of language. Proponents of mathematical Platonism claim that positing numbers offers a way of describing the conditions under which math-ematical claims are true or false. According to mathmath-ematical Platonism, there are true mathematical claims and those claims are true because they describe a domain of abstract mathematical objects. But is mathematical Platonism a good explanation of the conditions under which mathemati-cal claims are true? Some philosophers, such as van Fraassen, cannot see the relevance of such posits to our practices of counting and measuring.

The issue, then, is how the theories of the modal realist or the mathemati-cal realist are any better placed than astrology. If a given philosophimathemati-cal theory is a poor explanation, then applying it to many phenomena will not make it a better explanation. It will just be using the same poor expla-nation more widely. That is not shedding the light of explaexpla-nation. It is spreading the muck of obscurity.

We might reasonably reject astrological explanations as poor expla-nations because “we need to appeal to objective nomic relations, causal relations, or other sorts of physical mechanisms if we are to provide adequate scientific explanations” (Salmon 1989, 145). But just as astrology does not meet this requirement on explanation, neither do modal realism

4 See Swoyer (1979) for a reply.

nor mathematical Platonism. Modal realism rightly does not claim that causal relations or laws of nature hold between Lewisian possible worlds where there are talking donkeys and people in the actual world think-ing about talkthink-ing donkeys. Likewise, mathematical Platonism rightly does not claim that such relations hold between numbers not located in space-time and what people count or measure in the actual world.

At some times, there have been respectable scientific theories that have posited certain phenomena although they have not been able to specify the mechanisms supposedly responsible for these phenomena. For exam-ple, for some time after it was formulated genetic theory was unable to specify the mechanism whereby genes produce inherited characteristics.

Nevertheless, there were good prospects for finding these mechanisms and the search for them has often turned out to be successful, as it was in the case of genetic theory. In the case of modal realism and mathematical Platonism, however, there is no prospect for finding a mechanism medi-ating between the modal or the mathematical and us, as modal realists and mathematical Platonists would themselves acknowledge.