"Now free trade is not a theory in any sense of the word. It is only a mode of liberty; one form of the assault (and therefore negative) which the expanding intelligence of the present is making on the trammels which it has inherited from the past."
~ William Graham Sumner, from his 1885 book, Protectionism: the -ism Which Teaches that Waste Makes Wealth. Hat tip Don Boudreaux, who adds:

Sumner is exactly correct that domestic citizens’ freedom to trade with foreigners is no more a theory than is women’s freedom to trade with men, or blue-eyed people’s freedom to trade with brown-eyed people.
    We can and do use economic theory to better understand patterns and specific effects of international trade, just as we can, and sometimes do, use economic theory to better understand patterns and specific effects of purely domestic changes in the trading arrangements of some groups with others. But the case for a policy of free international trade is no more esoteric than is the case for a policy of free inter-eye-coloured trade or free inter-hair-coloured trade. That voluntarily struck trades between citizens of, say, the United States and citizens of Mexico increase the well-being of all parties to these trades without causing economically relevant harm to anyone should be no more controversial or notable than is the fact that voluntarily struck trades between blue-eyed people and brown-eyed people increase the well-being of all parties to these trades without causing economically relevant harm to anyone.
    And yet, of course, the weapons in the protectionists’ arsenal are all aimed at destroying the clarity of vision offered about international commerce by sound economics.

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