why the abolition of economic barriers between the members of the federation is not only a welcome concomitant but also an indispensable condition for the achievement of the main purpose of federation.

Unquestionably, the main purpose of interstate federation is to secure peace: to prevent war between the parts of the federation by eliminating causes of friction between them and by providing effective machinery for the settlement of any disputes which may arise between them and to prevent war between the federation and any independent states by making the former so strong as to eliminate any danger of attack from without. If this aim could be achieved by mere political union not extended to the economic sphere, many would probably be content to halt at the creation of aessentially liberal economic regime is a necessary condition for the success of any interstate federation, it may be added, in conclusion, that the converse is no less true: the abrogation of national sovereignties and the creation of an effective international order of law is a necessary complement and the logical consummation of the liberal program. In a recent discussion of international liberalism, it has been rightly contended that it was one of the main deficiencies of nineteenth-century liberalism that its advocates did not sufficiently realize that the achievement of the recognized harmony of interests between the inhabitants of the different states was only possible within the framework of international security.[7] The conclusions which Professor Robbins drew from his considerations of these problems and which are summed up in