First, of course, price stability is one of the objectives for monetary policy set by the Congress and, indeed, is highly desirable in its own right. And, of course, the price level is the macroeconomic variable over which a central bank exerts the most direct control in the long run.
Second, in the long run price stability promotes high employment and low nominal interest rates - the other objectives set by the Congress - as well as productivity and  5  Throughout this talk I follow a common Fed practice in using the core personal consumption expenditure (PCE) deflator to measure inflation.