Do biologists infer to the best explanation?

The modern debate about scientific realism is to a large extent a debate about the reliability of inference to the best explanation (IBE). Proponents of anti-realism argue that IBE is inherently problematic. We cannot expect it to lead us to true theories, since it only picks the best of the available hypotheses, leaving us susceptible to unconceived alternatives. Newtonian physics was certainly a powerful explanation — until a patent clerk in Bern conceived a superior alternative, special relativity. Realists in turn defend IBE, arguing, for example, that IBE has become more powerful over time because the scientific community has grown; or that those parts of theories that fuel their explanatory success have actually proved stable over time; or that explanatory theories are strongly confirmed only if they made novel predictions.

In a forthcoming paper co-authored with Aaron Novick, we approach this debate in a different way. We concede that IBE is a dangerous method, just as anti-realists have argued. But biologists already recognize its dangers and insist on more stringent methodological standards before they accept hypotheses as established. Explanatory power is not enough. We propose that biologists instead adhere to versions of the vera causa standard. It requires that causes be shown to exist, to be competent to produce the kinds of effects ascribed to them, and to be responsible for particular instances of those effects. Until this standard has been met, the biological community accepts causal claims only provisionally, regardless of how powerfully they explain. We support this thesis by studying debates about the physical basis of heredity from the late 19th century (when multiple ingenious hypotheses failed) to the early 20th century (when Mendelian genes were localized to chromosomes) and finally to the middle of the 20th century (when DNA was shown to transmit at least some heritable traits). While explanatory power certainly served as a guide to the “pursuitworthiness” of hypotheses, it played little or no role in their acceptance. We thus de-emphasize the importance of explanatory power and emphasize instead the importance of detection and intervention, and of inferring causal competence by various experimental and observational methods. On this basis, we develop a new case for scientific realism about many (not all) claims in biology.

One distinction is crucial in this debate. We do not deny that scientific activity is often bound up with explanation. Once scientists have inferred the truth or likely truth of a hypothesis, they use that hypothesis in order to explain things. But IBE postulates something more: that we infer the truth or likely truth of hypotheses because they explain. This is where we disagree: Biologists seem to ask much more of their hypotheses.

The paper is titled “Presume it not: True causes in the search for the basis of heredity”. It is forthcoming in the British Journal for the Philosophy of Science, and a preprint is now available on the PhilSci archive. I like how this one turned out.