Diminishing marginal utility is a law of economics stating that as a person increases consumption of a product, while keeping consumption of other products constant. Diminishing Marginal Utility is the fact that each addition good or service consumed, creates a smaller and smaller amount of additional utility. There is a decline in the marginal utility that person derives from consuming each additional unit of that product (Investopedia, 2013).

three economic aspects in which the irrefutably true law of diminishing marginal utility plays an important role

(1) A rise in the money stock. A rise in the money stock must, for logical reasons, reduce the exchange value of a money unit. This is because the additional money unit can be used to satisfy an additional end that is necessarily less urgent than the satisfaction of the preceding end. A rise in the money stock will thus necessarily lead to a decrease in the marginal utility of the money unit (compared to the situation in which the money stock had remained unchanged). (Polleit, 2011)
As a result, a rise in the money stock can never be "neutral" in economic terms. It necessarily leads to a decline in its exchange value — when compared with a situation in which the money stock had remained unchanged; a
A monetary policy of increasing the money supply is therefore never "neutral": It necessarily lowers the exchange value of the money unit, and it necessarily benefits some people (namely the first receivers of the new money) at the expense of others (namely the late receivers of the new money).

(2) A lowering of the market interest rate. The pure market interest rate reflects societal time preference — which, in turn, is also implied in the axiom of human action. Time preference means that market agents value goods available today (present goods) more highly than goods available in the future (future goods).