Contingenza e impedibilità delle cause. Presupposti e implicazioni di un dibattito scolastico

According to Avicenna, while the action of causes is always necessary, the production of effects may be considered in different ways. With respect to its cause, each effect is necessary, but may be contingent due to the interference of prohibitive impediments. In itself, and in an absolute sense, each effect is contingent. This article deals with the transformations of this model in the Latin Scholastic debate from the end of the 13th to the early decades of the 14th century, taking into consideration Thomas Aquinas, Siger of Brabant, John Duns Scotus and Francis of Marchia. The first defends a kind of ‘providential’ determinism, admitting only a relative, or secundum quid, contingency of sublunary effects with respect to the First Cause. The second, in explicit opposition to Aquinas, upholds the absolute contingency of the world in Avicenna’s sense. Interestingly enough, Siger’s position seems to be implicated in the condemnation of March 1277, not for being too deterministic but for rejecting an absolute ‘providential’ determinism. The last two both refuse to ground true contingency in impedible causes, appealing instead to freedom of will.