From Rothbard's 1969 minibook:
Fortunately, a correct theory of depression and of the business cycle does exist, even though it is universally neglected in present-day economics. It, too, has a long tradition in economic thought. This theory began with the eighteenth century Scottish philosopher and economist David Hume, and with the eminent early nineteenth century English classical economist David Ricardo. Essentially, these theorists saw that another crucial institution had developed in the mid-eighteenth century, alongside the industrial system. This was the institution of banking, with its capacity to expand credit and the money supply . . . It was the operations of these commercial banks which, these economists saw, held the key to the mysterious recurrent cycles of expansion and contraction, of boom and bust, that had puzzled observers since the mid-eighteenth century.