The creation of the World Trade Organization in 1994 with its streamlined and highly automatic system of dispute settlement has left open the question of whether we can identify a theory of its legal system. This article posits the idea that such a theory can be discerned if we conceive of the WTO Agreement as protecting expectations about trade, facilitating adjustment to realities encountered in trade, and promoting interdependence between economic operators. Each of these purposes is implemented under the WTO Agreement by a specific instrument. In the case of expectations it is collective obligations, in the case of realities it is individual rights, and in the case of interdependence it is a combination of the foregoing two – a lex specialis. The tension in this arrangement resolves itself in the form of a dialectic between WTO and domestic law. The article goes on to posit some consequences of the theory for the broader corpus of public international law.