Lionel Robbins’ definition of economics helped to buttress the centrality that individual choice acquired after the Second World War. This, however, was an unintended consequence of his seminal work. Underlying his definition of economics, a novel approach to methodological individualism is advanced, in which the isolated individual plays the role of a temporary device useful for analysing more complex social phenomena. The paper outlines three types of methodological individualism, and argues that Robbins’ approach cannot be classified under any of them; we thus propose a different category, that of ‘first-step individualism’. Robbins’ rationale for focusing on the isolated individual is not that social phenomena can be reduced to individual behaviour, but rather that this is the best starting point for economics, if it is to progress and be able to deal with more complex phenomena in the future.