In recent years, scholars have re-examined the innovative use the Mishnah makes of mental categories to determine legal outcomes. They suggest that this phenomenon reveals a new kind of subjectivity which is related to the prominence that the inner self receives in Late Antiquity, especially in Stoic philosophy. In this article I claim that the self formed by the Mishna is markedly different from the Hellenic self. The thoughts and deeds of the subject formed by the Mishnah are on the same plane, making for a 'flat' subject. There is no inner world which is fundamentally different than the outer one, such as the one we find in contemporary Hellenistic philosophy. This is, furthermore, a phenomenon of rabbinic halakhah, rather than of rabbinic discourse in general. The halakhic practice does not just regulate an inner world formed somewhere else, but takes part in forming a unique legal subject; one that is made to fit its regulatory discourse.