Building on systems theory and the economics of law, this paper argues that evolutionary models can explain certain features of common law reasoning, in particular the way that the doctrine of precedent operates to combine stability with change. The common law can be modeled as an adaptive system which coevolves with its environment, which in this context consists of the political and economic systems of a given society. The common law responds to signals from the economy and from politics (‘cognitive openness’), while retaining its distinct mode of operation (‘operative closure’). A version of the variation, selection, retention algorithm operates at the level of legal decision-making. Theories of legal evolution which stress selection and variation at the expense of inheritance describe only part of the process of legal change and are prone to teleological accounts of evolution to efficiency. Focusing on inheritance or retention helps us to see that the common law can only be qualifiedly adaptive, at best, and that many inefficient rules will persist and survive even in the face of selective pressures. The relevance of this approach is illustrated by an examination of the leading decision in the English (and Scottish) law of tort (or delict), Donoghue v Stevenson, and its implications for some influential accounts of legal evolution, including legal origin theory, are explored.
Deakin, Simon, Law as Evolution, Evolution as Social Order: Common Law Method Reconsidered (August 7, 2015). University of Cambridge Faculty of Law Research Paper No 43/2015.