The problem of the State’s part in economic life has been frequently debated since the day when John Stuart Mill devoted the last section of his ‘Principles of Political Economy’ to this subject. But the problem is not hackneyed, because, with changes in economic circumstances and in the political outlook, it takes on a new form from decade to decade and needs continual restatement. It does not lend itself easily to scientific discussion, for it involves both political and economic considerations; and in controversy these two aspects are often confused, so that a judgment which has really been determined by political opinion is made to appear as though it were a conclusion derived from a process of economic reasoning. Now no-one will contend that economic doctrine itself enables us to decide whether this or that action by the State in the economic field is justifiable or not. A judgment of that nature must depend upon many factors outside the province of economics. For example, those who hold the views of the early radicals, who believed that the State’s functions should be limited to providing a sound currency, enforcing contracts, and defining property rights, naturally deal with any question of intervention not upon economic grounds but in the light of their own philosophy.