The laws of any science ought to (1) accurately explain the occurrence of some phenomena in the past or present and (2) predict that such phenomena will occur again in the future. If a law fails in one of these two endeavors, then some limitation prohibits the application of the law. Hence, there is good reason to eliminate that law in part or in total.
The aim of Rosenberg’s article is to determine whether prediction in biology is limited. First, he contends that prediction in biology is severely limited because based upon a functional solution it is not possible to predict the structural solutions to biological problems of future adaptation. Second, Rosenberg believes that the law of natural selection is the only law in biology because it seems to have successfully led to the discovery of new phenomena. Finally, he considers how valuable the role of historical inference is to evolutionary biology.
1. Biology as an historical discipline
Let us begin with Rosenberg’s claim that biology is a historical discipline. The main concern of biology is not to formulate predictions or laws but to offer a description of historical events. Rosenberg recognizes that this approach stems from Darwin’s own conception of the theory of natural selection “as being in large measure a historical account of events on this planet and… not a body of empirical generalizations…” (Rosenberg 2000, p. 66). If history is the central focus of evolutionary biology, then two questions that must be answered. First, what kind of understanding can biology secure if its explanations are historical? All that a historical account can offer is a mere chronicle of events, so one would be hard pressed to attempt to explain why a sequence of events obtains. For Rosenberg, the inescapable demands of causal explanations leads back to the theory of natural selection (see below). Second, why do we want to know the actual histories of biological processes? Rosenberg believes that history is required for complete understanding in biology because biological theories can only be tested retrospectively within periods of varying length. Therefore, he concludes that biology is a historical discipline because the main principles – i.e. the theory of natural selection – are the “only transtemporally exceptionless laws of biology" (Rosenberg 2000, p.71).
If all biological theories can provide is an account of processes, then what is the scope of biological theorizing? Without diverse means to predict future occurrences, evolutionary biology provides nothing more than a catalog of historical events. It would seem that the range of biological theorizing diminishes exponentially if all that biologists could rely upon is the theory of natural selection.
2. Natural selection as the only law in biology
Rosenberg believes the only law in biology is the law of natural selection. Despite the fact that the theory of natural selection is a generalization connecting functional kinds, the primary reason for calling natural selection the only law in biology is that it seems to have consistently led to the discovery of new phenomena. Rosenberg writes, “Though sometimes stigmatized as Panglossian in its commitment to adaptation, evolutionary theory’s insistence on the universal relentlessness of selection in shaping effects into adaptations repeatedly has led to the discovery of remarkable and unexpected phenomena" (Rosenberg 2000, p. 63). Another reason why natural selection is the only law in biology seems to be that: if there were no “laws,” then an entirely new account of the nature of biological understanding would require a theoretical model. A typical theoretical model will give way to a general theory, but this does not happen in biology because biological models are not empirical generalizations. “Unlike physical science, where models are presumed to be way stations toward physical truths about the way the world works, there can be no such expectation in biology,” says Rosenberg (2000, p. 65). The biological model, if left unchecked, would attempt to explain too much based upon shaky foundations.
Rosenberg’s argument that biological models do not work because they would have to generalize from empirical facts is confusing. Rosenberg never seems to offer a reason why such generalizations are impossible, though he expects us to believe that they are. It is not sufficient to say that one cannot derive generalizations from empirical facts, period. There must be some reason or intuition for rejecting such a claim, which Rosenberg does not seem to provide. Does Rosenberg believe that a law in biology must imply necessity?
3. Prediction in biology
Finally, Rosenberg believes prediction in biology is severely limited. In biology, natural selection picks variants by some of their effects, usually the effects that are most advantageous to the individual. When natural selection anticipates variants to become packaged together into larger units, the adaptation becomes functions. The nature of this mechanism cannot discriminate between differing structures with similar effects. If this is the case, then there can be nothing close to a strict law in any science that “individuates kinds” by selected effects. Rosenberg writes, “If selection for function is blind to differences in structure, then there will be nothing even close to a strict law in any science that individuates kinds by selected effects, that is by functions” (Rosenberg 2000, p. 59). By distinguishing between functional and structural solutions, Rosenberg believes that it is not possible for a functional solution to predict the structural solutions to biological problems of future adaptation.
For cases where one cannot observe the physical features of an object, it seems that we can at least identify presumptive effects, and thereby assert a causal role description. Rosenberg says, “We may conclude that any science in which kinds are individuated by causal role will have few if any exceptionless laws” (Rosenberg 2000, p. 60). It seems to follow that no strict law can link either the observable world or nonobservable world with some exceptionless generaliziation, i.e. law, because of biology’s reliance on functional individuation.
Perhaps the absence of strict laws will not restrict biology in this way. For example, some may believe that ceteris paribus generalizations have explanatory power because they bear nomological force, but a good argument against such a claim says that a nonstrict law, such as ceteris paribus generalizations, requires strict laws to underwrite them. If there are no strict laws, then there are no nonstrict laws. According to Rosenberg, the only way to legitimize inexact ceteris paribus laws is through the existence of independent interfering factors. Independent interfering factors explain phenomena distinct from those the ceteris paribus generalization is invoked to explain. Even if independent interfering factors are introduced, this still requires the existence of strict laws. In biology, however, functional individuation precludes strict laws, so there are no nonstrict ones either.
The only way out of this conundrum is to drop functional individuation altogether. Rosenberg sees this option and proceeds to tell us that such a choice will result in a reduction of biology to “organic chemistry.” So, all that is left of laws in biology is the theory of natural selection because it is the only generalization that has consistently led to the discovery of new phenomena. Why should all generalizations, in order to be effective and to be considered “laws,” consistently lead to the discovery of new phenomena? Some may contend that in order for generalizations to be effective and considered “laws” they only need to predict the occurrence of future events. The prediction of these future events do not have to be entirely correct, but they should be as accurate as possible. Derivative explanations can explain away the occurrence of anomalies. Anomalies, then, would not disrupt the force and scope of the prediction. Also, what is unclear in Rosenberg’s explanation is why the reduction to history is more acceptable than the reduction to organic chemistry? In the final part of the paper, Rosenberg argues that biology is a historical discipline and seems to reduce evolutionary biology to a study of history. Although this seems like a correct move, the question remains: why not reduce biology to chemistry or one of the other physical sciences? What is it that makes history more acceptable than the physical sciences? Is it that the study of biology resembles history more than the physical sciences? Simply because a and b are similar does not mean that a can be reduced to b, or vice versa. The claim that biology is reducible to history needs further clarification before everyone jumps on the Rosenberg bandwagon.