In their work Monetarists draw a lot on Classical economics . They re-evaluated the Quantity Theory of Money and argued that increases in the money supply would cause inflation. This view was backed up by a substantial body of empirical evidence. They would therefore argue that to reduce inflation, the growth in the money supply needs to be controlled.
Monetarists vary in their precise beliefs on expectations.
Some believe that expectations adjust so quickly that any policy change will immediately be taken into account by people, and there will therefore be no short-term adjustment. This school of Monetarism is known as 'rational expectations'. More moderate Monetarists accept that there may be an adjustment period, and so policy changes may have temporary or short-term effects on the level of output.