Money and liquidity are not synonymous. They have reciprocal relations but, on several occasions, it is important to distinguish between the two concepts. A brief review of the theories of the demand for money, as is done in this document, serves to identify those circumstances. The review ends with Keynes′s theory. Keynes's contribution to monetary theory is significant. Stands out, in particular, his thesis concerning a dominance of the preference for liquidity in the demand for money if bearish expectations are prevailing with respect to the debt securities prices. Such expectations "inflate" (and distort the function of) the demand for money.