In his later career Ingram became interested in the nascent disciplines of sociology and economics. He was not a trained economist but rather a sociologist and his early economic writings dealt mainly with the Poor Law. He was a spokesman for historical economics in Britain and influenced many contemporary social and economic thinkers at that time in Great Britain, the United States, and continental Europe. His attack on classical economics encompassed its methodology and its conclusions. Ingram played an important role in the English Methodenstreit (Battle of methods), (closely associated with the Werturteilsstreit). In his 1888 "History of Political Economy" he used the term "economic man" as a critical description of the human being as conceived by economic theory, and he may have coined the term. From 1891 to 1896 Ingram wrote entries in "Palgrave's Dictionary of Economics". He was president of the Statistical and Social Inquiry Society of Ireland between 1878 and 1880 and took over as President of the Royal Irish Academy when William Reeves died in 1892.