This paper is devoted to Sextus’ target in Against the Arithmeticians : the ἀριθμητικὴ τέχνη. After a brief sketch of M IV’s content, we make an inquiry on the nature of such a discipline. Firstly we tackle the general question of what was the ἀριθμητική τέχνη in Antiquity. Once we are clearer on that – and thus on Sextus’ target in M IV, we explore its relationship to the other disciplines attacked by Sextus in his Against the Professors. This ultimately leads us to shed light on an important implicit assumption of Sextus’ attitude towards the sciences.