I defend the claim, made in a previous paper, that a Humean can be a contractarian‘, against the criticisms of Anthony de Jasay. Jasay makes a categorical distinction between ordered anarchy‘ (which he associates with Hume) and `social contract theory‘. I argue that Hume’s political position was conservative, not anarchist. On Hume’s analysis, a convention is an implicit agreement; the concept of convention is more general than, rather than distinct from, that of agreement by exchange of promises. Hume justifies political obligation by treating established forms of government as conventions in this sense.

In this paper I argue, contrary to Hartmut Kliemt, that it is possible to be both a Humean and, in James Buchanan’s sense, a contractarian. Hume sees principles of justice and political allegiance not as actual or hypothetical products of explicit agreement, but as conventions that have emerged spontaneously. However, it is fundamental to Hume’s analysis that conventions are mutually advantageous, and hence cognate with agreements. The core idea in Buchanan’s contractarianism is that the proper role of government is to implement voluntary exchanges between individuals, not to define and maximise a unified conception of social welfare. Although real politics cannot be based entirely on unanimous agreement, the voluntary exchange approach provides a valuable structure for normative economics.