In this article, the notion of the secular is defended as a meaningful and relevant concept in order to determine the role of theological reasoning in the public sphere. For this purpose, in the first section, it is shown that John Duns Scotus already developed a provisional account of the secular and, moreover, provided it with a theological justification. The second section starts off with a brief sketch of the secular’s main characteristics as they can be deduced from Scotus’s account. (...) Building on Thomas Pröpper, it is demonstrated how a transcendental analysis of freedom as the basic rationale of the secular brings to the fore a fundamental ethical principle as well as an idea of the secular’s ultimate destination. Theological reasoning in the public sphere or public theology, so it will be argued, aims primarily at making visible the ethical implications and the ultimate destination of the secular. (shrink)