Alfred Mill

Economics is the study of how individuals, institutions, and society choose to deal with the condition of scarcity.

Scarcity is the universal condition that exists because there is not enough time, money, or stuff to satisfy everyone’s needs or wants.

Capital is physical stuff used to make other stuff, and investment is the money spent on buying that stuff. To make capital, you have to have capital. Because capital is always purchased with borrowed money, it incurs an interest payment.