Physicalism appears to undermine the autonomy of ‘special sciences’ such as biology, and to leave little room for proprietary biological laws or causation. Mendel’s ‘Laws’ are so-called because they are fundamental to the subject-area, but since they describe causal processes that are wholly physical in nature, they seem to reduce to physical laws, given certain propositions about the composition of DNA. The same goes for other principles of the biological sciences.
This argument has been challenged by Hilary Putnam, on the grounds that good explanations, for instance in mathematical terms, could range more widely than any given physical realization. Putnam argues that mathematics could thus have an autonomous role in science despite physicalism. Putnam’s insight has been applied to classical genetics by Philip Kitcher. A gene is a unit of inheritance that passes unchanged from parent to offspring according to certain rules. It is these rules that are essential to understanding inheritance, not details of interaction in the DNA substrate. Putnam and Kitcher here employ a notion similar to Aristotle’s ‘formal causes’ – functional and structural determinants of biological characteristics that are somewhat independent of material constitution.
There are other conceptions of laws to be found in philosophy of science. Some think that they are propositions with the capacity to impart axiomatic structure to what is known about a domain. The principle of natural selection plays this role in biology, though it is a priori. Again, some think that laws are necessary truths: on cladistic systems of classification, the proposition that the common raven is a bird is arguably a law under this understanding.
The nature of causal patterns in natural selection has been a matter of some discussion recently. The view that individual-level causes are sufficient to explain selection-outcomes is tempting to the reductionist, but distorts the explanatory aims of evolutionary theory. Clearly, evolutionary theory requires population-level causes. On the other hand, it has been questioned whether natural selection itself should be understood as a ‘force’ acting on a population, somewhat in the same manner as gravitation acts on a body. Statistical views of natural selection seek alternatives to this way of understanding selection.
Finally, what are biological entities? Some ontologies admit no priority among collections of atoms – the argument is that an organism, for instance, is nothing more than such a collection. Many biologists, however, treat of composite entities as internally organized complex systems. On this view, cells, organisms, populations, and ecosystems have privileged ontological status.
A Mathematical Apriorist Answers Philip Kitcher