This chapter takes us to the start of the 1930s, to explore the colonial production of knowledge on mental illness in mandate Palestine. It does so not through the writings of any psychiatric expert, but rather the report on the 1931 census and its extensive analysis of the return of the ‘insane’ population. Rooted in a very particular encounter around mental illness – between enumerator and enumerated – the census report’s analysis, and the debates surrounding it, reveals how the question of mental illness could be used to locate both Palestine, and its different communities, in relation to empire, development, and modernity. This chapter eschews the usual focus on identity in relation to the colonial census to instead foreground translation: from myriad terms in multiple languages to the single term – ‘insanity’ – adopted by the report; from the often messy testimonies of the enumerated to the record of the enumerator; and from encounter into theory.