"Under existing conditions in the civilized world, the great struggle among men is for the possession of wealth. Would it not then be irrational to expect that the science which treats of the production and distribution of wealth should be exempt from the influence of that struggle? Macaulay has well said that if any large pecuniary interest were concerned in disputing the attraction of gravitation, that most obvious of all facts would not yet be accepted. What, then, can we look for in the teaching of a science which directly concerns the most powerful of "vested rights" — which deals with rent and wages and interest, with taxes and tariffs, with privileges and franchises and subsidies, with currencies and land tenures and public debts, with the ideas on which trade unions are based and the pleas by which combinations of capitalists are defended? Economic truth, under existing conditions, has not merely to overcome the inertia of indolence or habit; it is in its very nature subject to suppressions and distortions from the influence of the most powerful and vigilant interests. It has not merely to make its way; it must constantly stand on guard."