In this chapter I want to argue that one particular science faces limits that do not confront other sciences, and that these limits reflect a combination of facts about the world and facts about the cognitive and computational limitations of the scientists whose business it is to advance the frontiers of this science. The science is biology, and the limitations I claim it faces are those of explanatory and predictive power. In the first part of this chapter I advance a contingent, factual argument about the process of natural selection which destines the biology in which we humans can take an interest to a kind of explanatory and predictive weakness absent in our physical science. I then go on to show how these limitations are reflected in at least two of the ruling orthodoxies in the philosophy of biology: the commitment to the semantic approach to theories, and to physicalist antireductionism.

If I am correct about the limits to biological knowledge, we must face some serious issues in our conception of what scientific adequacy and explanatory understanding consist. My claim is that biology is far more limited in its ultimate degree of attainment of scientific adequacy than are the physical sciences, because the only generalizations of which biology is capable will not provide for the sort of coordinated improvement in explanation and prediction which characterizes increasingly adequate science. This fact about biology reflects as much on the biologist as it does on the phenomena the biologist seeks to explain and predict. Were we much smarter, physics and chemistry would remain very much as they are, but biology would look much different.