Marshall was one of those who used utility analysis, but not as a theory of value. He used it as a part of the theory to explain demand curves and the principle of substitution. Marshall's scissors analysis – which combined demand and supply,that is utility and cost of production, as if in the two blades of a pair of scissors – effectively removed the theory of value from the center of analysis and replaced it with the theory of price. While the term "value" continued to be used, for most people it was a synonym for "price". Prices no longer were thought to gravitate toward some ultimate and absolute basis of price; prices were existential, between the relationship of demand and supply.
Marshall's influence on codifying economic thought is difficult to deny. He popularised the use of supply and demand functions as tools of price determination (previously discovered independently by Cournot); modern economists owe the linkage between price shifts and curve shifts to Marshall. Marshall was an important part of the "marginalistrevolution;" the idea that consumers attempt to adjust consumption until marginal utility equals the price was another of his contributions. The price elasticity of demand was presented by Marshall as an extension of these ideas. Economic welfare, divided into producer surplus and consumer surplus, was contributed by Marshall, and indeed, the two are sometimes described eponymously as 'Marshallian surplus.' He used this idea of surplus to rigorously analyse the effect of taxes and price shifts on market welfare. Marshall also identified quasi-rents.
Source:(www.en.wikipedia.org)
