In his landmark book "Chance and Necessity: An Essay on the Natural Philosophy of Modern Biology," Jacques Monod seeks to articulate and then to resolve what he perceived to be a paradox afflicting modern biology: organisms both must be and can’t be purposive systems. The purposiveness of organisms, he claims, can by explained exhaustively by chance mutations to the otherwise invariant chemical basis of life: “Pure chance, absolutely free but blind, at the very root of the stupendous edifice of evolution” (Monod 1971: 112). In tracing evolutionary biology’s commitment to chance back to its methodological roots, Monod is echoing the Pre-Socratic atomist philosopher Democritus, who Monod credits with holding that everything in the world is the fruit of chance and necessity. Monod’s choice of philosophical avatar is apt and telling. Modern evolutionary biology is thoroughly neo-Democritean; like its atomist precursor, it allows no explanatory appeal to purposes. This, I maintain, is current evolutionary biology’s principal weakness. I attempt to develop in outline, a neo-Aristotelian conception of evolutionary biology, one that gives the purposiveness of organisms a central explanatory role.
Denis Walsh is Canada Research Chair in Philosophy of Biology in the Department of Philosophy, the Institute for the History and Philosophy of Science and Technology, and the Department of Ecology and Evolutionary Biology, at the University of Toronto. He gained his PhDs from McGill University, and King's College London. His research interests are in the nature of biological explanation, evolutionary population dynamics, and the place of development in evolutionary theory. He is currently completing a book manuscript provisionally entitled "Organisms: A Philosophical Introduction."