The Austrian School of Economics Sees the Interest Rate as a Real Phenomenon, but the Keynesian Liquidity Preference Theory Sees the Interest Rate as a Monetary Phenomenon

However, this changed with the work of the economists of the Austrian School of Economics and the (neo-)classical school. They interpreted the interest rate as a real phenomenon.  As such, the interest rate phenomenon would not be related to the existence of money as such. They showed that even in a barter economy there would be an interest rate. . . .

The interpretation of the interest rate as a real phenomenon was challenged by the work of John Maynard Keynes (1883–1946). According to his liquidity preference theory, the interest rate is a monetary phenomenon, determined by the supply of and demand for money.

--Ansgar Belke and Thorsten Polleit, Monetary Economics in Globalised Financial Markets (Berlin: Springer-Verlag, 2009), 151-152.