Of the many challenges theology faces, one is its own ability to cut off the branch it sits on. Yet this is what the doctrine of the noetic effects of the fall can do. In most traditions, but within Protestantism especially, the insistence that sin vitiates all human faculties including reason, creates a significant problem for theologians: how can we hope to do justice to our task of using reason to talk of faith, if the tool of our reason is so radically broken? As regards interdisciplinarity, this raises further interesting questions. Of course there is little theological agreement over the extent of the noetic effects of the fall, and in general those who are most optimistic about the continued role of reason tend to be the most enthusiastic about embracing insights from other disciplines - most notably philosophy. On the other hand, those who most strongly emphasise the brokenness of the ratio - I am thinking especially of Luther and Barth - tend to stress the problems inherent in the other disciplines and their subjection to delusion. In such a vision, human endeavours such as philosophy, the social sciences or ethics, build upon foundations always already undermined by the radical effects of sin, and therefore require the corrective of a self-confident theology based in revelation. My proposal is that we migh take this the other way around: that an insistence on the radical fragility of human faculties based on Luther's insights, might actually suggest theology needs the other disciplines. This is not because human insight and enquiry are so powerful that theology relies upon them (what I would call a positive vision of interdisciplinarity), but because theology, like the other disciplines, is an hermeneutical project beset by its own sinfulness. This means theology needs all the help it can get. Sin renders all intellectual endeavour fragile and unstable, and so a negative interdisciplinarity is a source of checks and balances in the intellectual ecology.