 Lewis was a scholar of Greek history.Much of his work was concerned with inscriptions, but he insisted (in particular in an address to the epigraphic conference in University of Cambridge in 1967) that epigraphy should not be an activity for initiates only, but should be one means among others to the end of understanding the ancient world as fully as possible.He took a particular interest in what could be learnt from texts which even those who venture into the world of inscriptions find intimidating, accounts of expenditure and inventories of temple treasures; and this interest was extended to oriental documents, in particular the fortification tablets from Persepolis.