Meaning: In the long run we will all be dead.

The following is a relevant introduction to Keynes:

Keynes (1883-1946) was originally a free trade theorist. Until the late 1920s, he still believed in the traditional free trade theory and believed that protectionism It does nothing for domestic economic prosperity and job growth. Even when he was debating the issue of German reparations with Swedish economist Ohlin in 1929, he insisted that the balance of payments would automatically restore balance through changes in domestic and foreign price levels.

When his masterpiece "The General Theory of Employment, Interest and Money" ("The General Theory") was published in 1936, Keynes reversed his past position and instead emphasized the trade balance Regarding the impact on national income, I believe that if protective policies can bring about a trade surplus, it will definitely help increase investment levels and expand employment, and ultimately lead to economic prosperity.

The above information refers to Baidu Encyclopedia - Keynes