The doctrine of William of Occam (d. cir. 1349) has had an astonishingly negative effect on the very faith that it tried to reinforce. Ironically, many "papal Catholics," i.e., those who consider themselves absolutely loyal to the pope, use Occam's distortion of Duns Scotus's emphasis on the primacy of the Will to support their position.
As far as they are concerned, something is true because the pope says it, not because the Holy Spirit has granted the pope as pope a special power to discern truth in the area of faith and morals. No, the ultra-ultramontane insists, every utterance of the pope is infallible because he's the pope.
Occam, however, not only rejected the correct understanding of papal infallibility (and would have been astounded that his philosophy was being used to assert even an incorrect understanding of the doctrine), he believed that the papacy itself is heretical as an institution. As George Sabine analyzed Occam's position,
"For William papal sovereignty is, from the standpoint of Christianity, a heresy, and from the standpoint of policy, a disastrous innovation that has filled all Europe with strife, has destroyed Christian freedom, and has led to an invasion of the rights of secular rulers. . . . His primary purpose was to assert the independence of the whole body of Christian believers against the pretensions of an heretical pope." (George H. Sabine, A History of Political Theory, Third Edition. New York: Holt, Rinehart and Winston, 1961, 205.)
Not surprisingly, Occam joined with Michael of Cessena, Father General of the Franciscans, in redefining private property from a natural right to prudential matter. This, along with intemperate attacks on the papacy resulted in Michael of Cessena's excommunication in 1328 and the issuance of the papal bull Quia Vir Reprobus ("That Evil Man") in 1329. Occam had already been condemned as a heretic in 1326.
The conclusions that necessarily follow Occam's philosophy are surprisingly modern — or, perhaps, not so surprising once we realize that virtually the whole of political, social and religious life is, consciously or not, based on his thought. As Heinrich Rommen explained,
"For Occam the natural moral law is positive law, divine will. An action is not good because of its suitableness to the essential nature of man, wherein God's archetypal idea of man is represented according to being and oughtness, but because God so wills. God's will could possess the same binding force as that which is now valid — which, indeed, has validity only as long as God's absolute will so determines. Law is will, pure will without any foundation in reality, without foundation in the essential nature of things. Thus, too, sin no longer contains any intrinsic element of immorality, or what is unjust, any inner element of injustice; it is an external offense against the will of God." (Heinrich Rommen, The Natural Law. Indianapolis, Indiana: Liberty Fund, Inc., 1998, 52.)
In other words, if you can find an authority to say what you want to hear, then it must be authentic Catholic teaching. Nothing is objectively wrong if you can find someone to say so, or if it interferes with something you want.
Also, if you can bully someone or browbeat him or her into saying what you want, that works, too. That proves your interpretation of God's Will must be right because your faith is great, and your coercive power is even greater. Might makes right.
Further, if the State replaces God (as it has to a large extent in our day), then whatever the State says is legal is also moral, automatically. As Keynes declared, the State has the power to "re-edit the dictionary." This replaces God with the State as the Great Re-Editor, and makes everything okay if the State says so. As for the reason that the popes have taught is the means by which we discern both the existence of God and the basic precepts of the natural law (Humani Generis, §§ 1-2), it is discarded. Consequently, as Rommen explained,
"Moral goodness consists in mere external agreement with God's absolute will, which, subject only to His arbitrary decree, can always change. . . . Man sins, therefore, because and only so far as a positive law, by which he is bound, stands over him. God, on the other hand, cannot sin because no law stands above Him, not because it is repugnant to His holiness. Hence there exists no unchangeable lex naturalis, no natural law that inwardly governs the positive law. Positive law and natural law, which indeed is also positive law, stand likewise in no inner relation to each other. The identity of this thought structure with The Prince of Machiavelli, with the Leviathan of Hobbes, and with the theory of will of modern positivism (the will of the absolute sovereign is law, because no higher norm stands above him) is here quite obvious." (The Natural Law, op. cit., 53.)
Thus, if your faith is great, then you must be right, and everybody who disagrees with you on anything is irredeemably evil. This is rather contradictory for an orientation allegedly based on amor instead of iustitia, but it follows logically from the shift from objective nature to subjective will.