Ludwig von Mises: The Causes of Economic Crisis (1931)

Credit expansion cannot increase the supply of real goods. It merely brings about a rearrangement. It diverts capital investment away from the course prescribed by the state of economic wealth and market conditions. It causes production to pursue paths which it would not follow unless the economy were to acquire an increase in material goods. As a result, the upswing lacks a solid base. It is not a real prosperity. It is illusory prosperity. It did not develop from an increase in economic wealth [i.e. the accumulation of savings made available for productive investment]. Rather, it arose because the credit expansion created the illusion of such an increase. Sooner or later, it must become apparent that this economic situation is built on sand.

Hat tip to John Hussman