In an essay with this title in Nature, Evelyn Fox Keller notes that physicists come from a tradition of looking for all-encompassing laws, and asks whether this the best approach to use when probing complex biological systems.
"How appropriate is it to look for all-encompassing laws to describe the properties of biological systems? By its very nature, life is both contingent and particular, each organism the product of eons of tinkering, of building on what had accumulated over the course of a particular evolutionary trajectory. Of course, the laws of physics and chemistry are crucial. But, beyond such laws, biological generalizations (with the possible exception of natural selection) may need to be provisional because of evolution, and because of the historical contingencies on which both the emergence of life and its elaboration depended.
Perhaps it is time to face the issues head on, and ask just when it is useful to simplify, to generalize, to search for unifying principles, and when it is not. There is also a question of appropriate analytical tools. Biologists clearly recognize their need for new tools; ought physical scientists entering systems biology consider that they too might need different methods of analysis — tools better suited to the importance of specificity in biological processes? Finally, to what extent will physicists' focus on biology demand a shift in epistemological goals, even the abandonment of their traditional holy grail of universal 'laws'? These are hard questions, but they may be crucial to the forging of productive research strategies in systems biology. Even though we cannot expect to find any laws governing the search for generalities in biology, some rough, pragmatic guidelines could be very useful indeed."