… is from page 182 of an excerpt of 1977 Nobel-laureate’s Bertil Ohlin ‘s 1933 book, Interregional and International Trade  – the excerpt appearing in William Allen’s edited 1967 collection, International Trade Theory: Hume to Ohlin :
A fundamental aspect of trade is that it places the demand of one region in touch with the supply of productive factors in the other.
DBx: Trade intensifies human cooperation and productivity. (In the bargain it also reduces the prospects of war.)
The protectionist wishes to deny to his fellow citizens these benefits – namely, opportunities to better satisfy their wants by availing themselves of whatever help is offered to them by foreigners.