This paper tries to consider what we can think of the theoretical issues of the subject and the ethical horizon after the death of the subject announced by structuralism and poststructuralism. In the field of theory since 1960s, one of the most important issues has been arranged around the relationship between the subject and the structure. Structuralists and poststructuralists attacked the dominant status of the subject by regarding it as the effect of ideological interpellation, linguistic signification, modern disciplinary regime, and psychological misrecognition. They were excellent in revealing the dynamics of the structural mechanism constructing the subject but had limitation to think of the subject only as a part of the very mechanism. Against this grain, Alain Badiou and Giorgio Agamben take upon the problem of the change which poststructuralists had considerable difficulties dealing with. Badiou emphasizes the subject as the faithful follower of the event and the truth, while Agamben tries to look for the way to expand the ethical horizon in terms of inactivation without restoring the subject like Badiou. Interestingly, both thinkers wrote important books on St. Paul, in which St. Paul plays as the conceptual persona enacting their thoughts theoretically. St Paul is referred to by Badiou as the revolutionary subject to break away from the existing situation of law, while treated by Agamben as an apostle to make the existing structure of the law inoperative.