 In 1952–1953, Aaron was invited to be Visiting Professor at Yale University.In 1956 he was able to study the third draft of Locke's "An Essay Concerning Human Understanding" at the Pierpont Morgan Library, which resulted in a substantial addition to the second edition of "John Locke", published in 1955.He was made a Fellow of the British Academy (FBA) and President of the Mind Association in the same year.