It challenged the theory that the vital interests of nations are conflicting, and that war is part of the inevitable struggle for life among them; the view that, in order to feed itself, a nation with an expanding population must conquer territory and so deprive others of the means of subsistence; the view that war is the 'struggle for bread.'[101] In other words, it challenged the economic excuse or justification for the 'sacred egoism' which is so largely the basis of the nationalist political philosophy, an excuse, which, as we shall see, the nationalist invokes if not to deny the moral law in the international field, at least to put the morality governing the relations of States on a very different plane from that which governs the relations of individuals. As against this doctrine _The Great Illusion_ advanced the proposition, among others, that the economic or biological assumption on which it is based is false; that the policy of political power which results from this assumption is economically unworkable, its benefits an illusion; that the amount of sustenance provided by the earth is not a fixed quantity so that what one nation can seize another loses, but is an expanding quantity, its amount depending mainly upon the efficiency with which men co-operate in their exploitation of Nature. As already pointed out, a hundred thousand Red Indians starved in a country where a hundred million modern Americans have abundance. The need for co-operation, and the faith on which alone it can be maintained, being indispensable to our common welfare, the violation of the social compact, international obligation, will be visited with penalties just as surely as are violations of the moral law in relations between individuals. The economic factor is not the sole or the largest element in human relations, but it is the one which occupies the largest place in public law and policy. (Of two contestants, each can retain his religion or literary preferences without depriving the other of like possessions; they cannot both retain the same piece of material property.) The economic problem is vital in the sense of dealing with the means by which we maintain life; and it is invoked as justification for the political immoralism of States. Until the confusions concerning it are cleared up, it will serve little purpose to analyse the other elements of conflict. What justifies the assumption that the predatory egotism, sacred or profane, here implied, was an indispensable part of the pre-war political philosophy, explaining the great part of policy in the international field?[102]