 John Duns Scotus (1265/66–1308) was the stoutest defender in the medieval era of a strongly libertarian conception of the will, maintaining on introspective grounds that will by its very nature is such that “nothing other than the will is the total cause” of its activity (QAM). Indeed, he held the unusual view that not only up to but at the very instant that one is willing X, it is possible for one to will Y or at least not to will X. (He articulates this view through the puzzling claim that a single instant of time comprises two ‘instants of nature’, at the first but not the second of which alternative possibilities are preserved.) In opposition to Aquinas and other medieval Aristotelians, Scotus maintained that a precondition of our freedom is that there are two fundamentally distinct ways things can seem good to us: as practically advantageous to us or as according with justice. Contrary to some popular accounts, however, Scotus allowed that the scope of available alternatives for a person will be more or less constricted. He grants that we are not capable of willing something in which we see no good whatsoever, nor of positively repudiating something which appears to us as unqualifiedly good. However, in accordance with his uncompromising position that nothing can be the total cause of the will other than itself, he held that where something does appear to us as unqualifiedly good (perfectly suited both to our advantage and justice)—viz., in the ‘beatific vision’ of God in the afterlife—we still can refrain from willing it. For discussion, see  John Duns Scotus, §5.2.