John Stuart Mill proved that a country with monopoly pricing power on the international market could manipulate the terms of trade through maintaining tariffs, and that the response to this might be reciprocity in trade policy. Ricardo and others had suggested this earlier. This was taken as evidence against the universal doctrine of free trade, as it was believed that more of the economic surplus of trade would accrue to a country following "reciprocal", rather than completely free, trade policies. This was followed within a few years by the infant industry scenario developed by Mill promoting the theory that the government had the duty to protect young industries, although only for a time necessary for them to develop full capacity. This became the policy in many countries attempting to industrialize and out-compete English exporters. Milton Friedman later continued this vein of thought, showing that in a few circumstances tariffs might be beneficial to the host country; but never for the world at large.