but rather some malign genius...

René Descartes : Meditationes de prima philosophia : Meditations on First Philosophy (from Prima : The First)

12. "Supponam igitur non optimum Deum, fontem veritatis, sed genium aliquem malignum, eundemque summe potentem & callidum, omnem suam industriam in eo posuisse, ut me falleret:"

[12.] "I shall, then, suppose that not the optimal God -- the font of truth --, but rather some malign genius -- and the same one most highly powerful and most highly cunning --, has put all his industriousness therein that he might deceive me:" (tr. George Heffernan, University of Notre Dame Press, 1990.)