William of Occam was the most prominent intellectual leader in an age which witnessed the disintegration of the old scholastic realism, the rise of the theological scepticism of the later middle ages, the great contest between pope and emperor which laid the foundations of modern theories of government, and the quarrel between the Roman curia and the Franciscans which showed the long-concealed antagonism between the theories of Hildebrand and Francis of Assisi; and he shared in all these movements.
In another way also Occam heralds the'dissolution of Scholasticism.
Still later Duns Scotus and Occam were both Franciscans.
In his writing Super potestate summi pontificis octo quaestionum decisions (1339-1342) Occam attacks the temporal supremacy of the pope, insists on the independence of kingly authority, which he maintains is as much an ordinance of.
He was one of the first to attack the realist doctrines of Duns Scotus, and is interesting mainly as the precursor of William of Occam in his revival of Nominalism.
The hypostatizing of abstractions is the error against which Occam is continually fighting.
Beside the theological and political works above quoted, Occam wrote Summa Logices (Paris, 1488, Oxford, 1675) commentaries on Porphyry's Isagoge, on the Categoriae, De Interpretatione and Elenchi of Aristotle.
As regards the existence (if we may so speak) of the universal in mente, Occam indicates his preference, on the ground of simplicity, for the view which identifies the concept with the actus intelligendi, rather than for that which treats ideas as distinct entities within the mind.
Treatises on poverty appeared on every side; the party of Occam clamoured with increasing imperiousness for the condemnation of John by a general council; and the Spirituals, confounded in the persecution with the Beghards and with Fraticelli of every description, maintained themselves in the south of France in spite of the reign of terror instituted in that region by the Inquisition.
And to assert its absolute sovereignty (Defensor pacis, c. 1352); while the Franciscan William of Occam (d.