For Smith, the act of saving drives investment, not consumption. Why? Because the wealth of the nation is its total income. Take what is used for the reproduction of labor (wages) out of this income, and what is left is profit. Profits are then reinvested in the economy via merchants' savings, which are lent out to the productive members of society (other merchants) to invest. Today we call this supply-side economics. Investment both drives consumption and makes consumption possible—not the other way around. Because of this "the greater part of it [income] will naturally be destined for the employment of industry." Underlying this worldview is a particularly Scottish psychology that is worth unpacking because it suggests why the idea of austerity has such moral force, even today.

Mark Blyth, Austerity, loc. 296