This is the seventh in a series of seven papers on interest rates and it covers the Wicksell hypothesis, the general interpretation of it, an alternative interpretation, how the alternative interpretation is reconciled with the general interpretation, and its fit with the Taylor rule. A modification to the Taylor rule is discussed. The seven papers cover: (1) what are interest rates?; (2) relationship of interest rates; (3) composition of interest rates; (4) interest rate discovery; (5) bank liquidity & interest rate discovery; (6) role of interest rates; (7) an optimal rate of interest: the natural rate.