In a recent interview with the New York Daily News, Democratic presidential candidate Bernie Sanders said he would renegotiate every trade deal made by the United States under new criteria. Sanders claims the U.S. can do this by negotiating trade deals based on equal and stringent labor and environmental standards.

It may seem meritable for Sanders to advocate for more equal standards between the U.S. and its trade partners, but in practice such an idea is faulty.

The Economist Magazine explained on April 2, 2016 that the U.S. middle class “would lose 29 percent of their purchasing power if America was closed to trade, but that the poorest would forfeit as much as 62 percent.” The reason is because free trade is necessary for countries to compete in a global economic environment. This increases productivity and lowers prices to allow consumers greater overall buying power.

Granted, it is true that existing trade networks are flawed, but Sanders’ proposals would cut off trade with the developing world. That kind of economic isolationism is exactly what plunged the world into the Great Depression during the 1930s.

It is easy for Sanders to advocate for the maxim of fair trade, but it is a completely different matter to understand its nuanced wisdom.

It is crucial that policymakers understand that wisdom because, as Richard Hauss of the Council on Foreign Relations wrote, “foreign policy begins at home.” Our reformation will determine our standing in a now multipolar world and free trade is an issue that the United States must get right in order to guarantee a bright future for our posterity.

A “political revolution” must have direction. However, when it comes to free trade, the Sanders campaign is only preaching desultory velleities.