He knew that students would not find microeconomics, with its emphasis on efficiency, interesting unless they were first convinced that the economy could achieve more or less full employment, that it need not relapse into depression.
He knew the only way he could get his students to learn microeconomics was to convince them their understanding of the economy was vital to their future ability to find jobs and maintain the national economy in the next 50 years. 
mnli hypothesis: He knew the only way he could get his students to learn microeconomics was to convince them their understanding of the economy was vital to their future ability to find jobs and maintain the national economy in the next 50 years.  premise: He knew that students would not find microeconomics, with its emphasis on efficiency, interesting unless they were first convinced that the economy could achieve more or less full employment, that it need not relapse into depression.