In the aftermath of the great financial crisis (GFC) a consensus has formed that economics needs to be reinvented, and most especially macroeconomics. In this article, a first lecture of macroeconomics provides students with a sound foundation. Using a graphical model we demonstrate that when net expenditures increase, the world economy expands with rising employment; and when net expenditures slow, so does the world economy. At the margin, expenditures can only be increased by injections of net deposits created by an increase in debt. Concluding this first lecture, students take away the insight that (rising) expenditures and debt are necessary for the world economy to grow, and that both the rate of unemployment and the rate of inflation are correlated to the change in debt.