Explanation in Archaeology: An Update Wesley C. Salmon Abstract: This paper presents some important recent developments in the philosophical theory of scientific explanation and considers their bearing upon issues concerning explanation in archaeology. It argues that, although the received view of Carl G. Hempel has been seriously undermined in various ways, the newer conceptions can be applied within archaeology. The result is that archaeologists now have available to them more sophisticated conceptions of scientific explanation than were available in the earlier days of the "new archaeology. " During the last few years I have been taking a fairly close look at some recent history of philosophy of science that has a direct bearing on archaeology.! The starting point is 1948, when Carl G. Hempel and Paul Oppenheim published their epoch-making article, "Studies in the Logic of Explanation." It attempted to provide an explicit and precise account of the so-called deductive-nomological pattern of scientific explanation. In my view, this essay marks the dividing line between the prehistory and the history of philosophical work on the nature of scientific explanation. To my utter astonishment I found that this article was virtually ignored for an entire decade after its publication. Then, quite suddenly, around 1957-58, it became the SUbject of intense critical discussion. What came to be called the new archaeology has its roots in the same period. During the 1950s, Lewis Binford, one of its chief founders, was a graduate student at the University of Michigan. One of his teachers, the famous cultural anthropologist Leslie White, advised him to find out what science is all about by studying the works of philosophers of 243 L. Ell/brae (ed.), Mf'/(I(II'I'/I (I (!O /Ogy, 243- 253 . © 1992 J(/(i11'I'I' 1\I'rlr/I I/III,' / 'I//JlISiJ f'i'.I', PI'tIlIN l/1I liJl' N l!liJ('f'/(illt /,I', 244 WESLEY C. SALMON EXPLANATION IN ARCHAEOLOGY 245 science. He took that advice.2 One of the key features of the new example, to explain an airplane crash the FAA looks for causes. Similarly, archaeology is its emphasis on the search for scientific explanations that to find an explanation of the abandonment of Grasshopper Pueblo, fit the deductive-nomological model. archaeologists seek the causes of the departure. Hempel and Oppenheim The Hempel-Oppenheim article is a preliminary study. Hempel (1948, p. 250), in passing, casually identified their deductive-nomological provided a much more full-blown account in his 1965 monographic essay, pattern of explanation with causal explanation. In his fully developed "Aspects of Scientific Explanation." This essay offers an induc­ theory, however, Hempel (1965, pp. 352-54) explicitly denies that causality tive-statistical pattern of scientific explanation which supplements the is in any way essential to explanation. Many philosophers have criticized earlier deductive-nomological model.3 Both of these patterns are "covering the received view in general for its neglect of causal considerations, and law models," in that each requires that explanations incorporate the in W. Salmon (1982) I argued at length for the importance of causality statement of a universal or statistical law of nature. A heavily in archaeological explanation in particular. watered-down treatment of scientific explanation was given in Hempel's The causal character of archaeological explanation has to be taken in little 1966 textbook, Philosophy of Natural Science. The general conjunction with a recognition of the basic statistical character of account-offered in full detail in "Aspects of Scientific Explanation" and explanations in the sciences-especially the behavioral sciences. In superficially in Philosophy of Natural Science-qualified, during the 60s archaeology, for example, one might appeal to the fact that a particular and 70s, as the received view of scientific explanation. It was this view hunting strategy is, in certain specific circumstances, more likely than that profoundly influenced the new archaeology. The influence can readily another to yield success. This is obviously a probabilistic relationship. be seen in Watson, LeBlanc, and Redman's Explanation in Archeology: People often maintain, of course, that underlying the statistical explana­ An Explicitly Scientific Approach (1971), the locus classicus of the new tions are deterministic causal relationships, and that we resort to statistical archaeology. Their commitment to the received view is reiterated in the considerations only because of our ignorance of these underlying causal second edition, published under the title Archeological Explanation: The relationships. My own view is that we need not make gratuitous Scientific Method in Archeology (1984). metaphysical assumptions of that sort. A more straightforward and Influential as these standpoints were, not all archaeologists were realistic approach is to try to develop a theory of probabilistic causality. persuaded by the new archaeology and not all philosophers of science A great deal of serious effort has been devoted to the elucidation of accepted the received view of scientific explanation. I shall not try to probabilistic causality, but the problem is not simple. For example, in trace the subsequent developments in archaeology, since I am not elaborating a version of probabilistic explanation that he calls aleatory qualified to do so. Nevertheless, I would like to say a little about explanation, Paul Humphreys (1981, 1983, 1989) has pointed out that, in developments in the philosophy of science concerning scientific explana­ the statistical context, we must make allowances for both contributory tion. The philosophical situation has changed markedly since the early causes and counteracting causes. In attempting to explain the abandon­ 1970s. ment of Grasshopper Pueblo, for example, we must take account of such The first point to emphasize is that the "received view" is no longer contributing factors as the occurrence of a fairly severe drought and such received. Indeed, there is widespread (though not complete) consensus counteracting factors as the existence of a highly developed stable among those actively working on scientific explanation that the. "received community. The situation becomes extremely complex when we realize view" of the 60s and 70s is basically unsound. I shall not go into the that, in some cases, two factors that qualify individually as contributing details of the philosophical arguments that have brought about this causes may, when they occur together, constitute a counteracting cause. change of attitude, but I would like to say a little about their upshot for Although one cannot say that a satisfactory account of probabilistic archaeology.4 To do so I shall briefly discuss two general approaches to causality has been developed, I think we can say that important progress scientific explanation. has been made in that direction.5 1. Causal explanation. It seems evident to common sense that, in many The recognition of causal aspects of scientific explanation does nothing cases, to explain some phenomenon is to find and cite its cause. For to undermine the covering law character of explanations. The causal 246 WESLEY C. SALMON EXPLANATION IN ARCHAEOLOGY 'I processes and interactions to which we appeal for purposes of giving an explanation, whether of a deterministic or a probabilistic sort, are well, perhaps, as economics, sociology, and psychology. Thoro NUll 1\ II Iii III governed by causal laws. the question of whether any distinctively archaeological blws ,'xll·H II lit " , 2. Explanation by unification. One idea-implicit in many works on then any legitimate archaeological explanation would have 10 (/(' p"llIl 11 11 scientific explanation, and made explicit by Michael Friedman (1974)-is laws from other scientific disciplines, and these laws wOllld Iii I 1\ /01, that science enhances our understanding of the world by providing unified unifying connections between a portion of archaeology and a l 1 \l1l1~ 1 11111 accounts of wide ranges of phenomena. Our understanding increases as other domain. Such explanations would thus exemplify the lInif'iI"III1!l" I d we reduce the number of independent assumptions required to explain archaeological phenomena with the phenomena in other rOil hllN I" a given body of phenomena. Friedman cites as an example the science, natural and/or behavioral. This must not, however, be tal«('" III kinetic-molecular theory of gases, which gives a unified account of a imply that explanatory unification cannot exist if laws peculill I II ' number of different gas laws-Boyle's law, Charles's law, Graham's law, archaeology are invoked in archaeological explanation. There might 1)( etc.-and connects them with other mechanical phenomena that can be bona fide archaeological laws that can themselves be explained by 1:lw/, explained by Newtonian physics. The search for broad unifying theories of other domains. The fact that optics is reducible to electromagJlet/1" has certainly been a major driving force in the history of science, and it theory does not imply that there are no laws of optics or that they aI'r has met with some striking successes in the natural sciences. not used in explaining optical phenomena.6 Explanatory unification often involves the reduction of one domain of Let us take a moment to compare and contrast causal explanationN science to another. When, for example, it was shown that visible light and unifying explanations. To provide a causal explanation of any given consists of electromagnetic waves that occupy a small segment of the fact, it is often necessary to get into the nitty-gritty details of the causal total spectrum of electromagnetic radiation, optics was reduced to mechanisms that produced the fact-to-be-explained. To explain the electromagnetic theory. Thereafter, it was not necessary to have two location and contents of a particular burial, for instance, it may be separate theories-one for optics and another for electromagnetic necessary to ascertain the age and gender of the individual interred, and phenomena-because Maxwell's theory of electromagnetism covered them to determine the cause of death.