Unlike physical objects, which can be accounted for as the necessary consequences of the operation of natural laws, living matter is the product of an essentially ad hoc process known as evolution. There is a fundamental difference between an explanation based on physics, chemistry and systemwide regulation and an evolutionary explanation. What makes living matter special is a history of change. Variation - rather than fixity - is of the essence. It is because of this that biology is unlikely eventually to have a mathematical structure all its own, say in the manner of theoretical physics.
