Adam Smith's The wealth of Nations (1776), along with the later works of David Ricardo, established the central concepts that are now recognized as classic liberalism. In this excerpt from The Wealth of Nations, Smith makes his case for free trade, arguing that goods should be purchased from the most efficient producer, regardless of the country of origin. The advantage of this type of trade is not only seen in the savings obtained for individuals and societies as a result of encouraging production by the most efficient producers, in addition, jobs will be shifted to the most efficient sectors of the economy. Unlike some contemporary proponents of free trade, Smith does not champion unconditional or unilateral free trade. Here he explains how national security concerns led him to sympathize with the Navigation Acts. He also concedes that in some cases it may be wise to neutralize the advantages some foreign governments give to their producers. Such actions, Smith warns, may backfire and damage long-term trade relations.