Studying economics for moral purpose, his most famous work advanced his form of welfare economics, as well as introduced the concept of price-elasticity of demand.  
He advanced the idea that economics should be understood like biological evolution, a method culminating in his partial equilibrium analysis.  Studying economics for moral purpose, his most famous work advanced his form of welfare economics, as well as introduced the concept of price-elasticity of demand.  His first published work was a review of the work of Jevons, while his first book, The Economics of Industry, was coauthored with his wife.  He was unable to produce a follow-up to his major work, and instead published 1919's Industry and Trade, and 1923's Money, Credit and Commerce. FTP, identify this pioneering economist, known as the teacher of Keynes and author of The Principles of Economics.
He advanced the idea that economics should be understood like biological evolution, a method culminating in his partial equilibrium analysis.  
Alfred Marshall