In the utility approach, Alfred marshall explains the Law of Diminishing Marginal Utility. This concept states when consumption increases, the marginal utility derived from each additional unit declines.
In Marshall's theory, the concept of utility is cardinal. The price that a consumer is willing to pay for a good is an indication of the utility of that good to the consumer. Total utility is the sum of the utility, which a consumer derives from the consumption of the different units of a good.