My purpose in this paper is to illustrate how we can understand that what the Christian tradition calls the peccatum naturae neither consists in a mere privation nor in the total corruption of nature. There is a widespread understanding that for Catholics the sin of nature consists in the privation of the gift of original justice –the complete order of the natural tendencies and their subjection to reason as a result of the elevation of our first parents to a state (...) of grace–, whereas Protestant denominations would in general terms understand that after the fall human nature was abandoned to a complete corruption. The two stances are sometimes seen as an either-or dichotomy. My intention is not theological, since I do not want to discuss or decide what Christians should believe in this matter, but I try to dig into the conceptual conditions under which we can coherently understand that our present condition is characterized by a twisted inclination of the will, which without destroying or totally corrupting human nature, still runs contrary to its proper good and cannot be considered as belonging or being inherent to it. I first present Thomas Aquinas’ understanding of the peccatum naturae as a moral defect. Then, I take recourse mostly to Rosmini’s work in order to better understand how there could be a moral weakness, which could be rightly called corruption, without implying that our moral condition is completely irrecoverable. (shrink)