or Ockham, William of, an English scholastic philosopher, and the great champion of Nominalism in the fourteenth century, was born at Ockham in Surrey in the latter half of the thirteenth century. He repaired to Paris at an early age, having been expelled from Oxford for exciting tumults among the students. On reaching that city he joined the ranks of the Franciscans, and sat at the feet of their great chief, Duns Scotus, "the most subtle Doctor." Nothing is known respecting Occam until he appeared as a public teacher in Paris. In this capacity he produced an extraordinary sensation. By the boldness of his speculations and the vehemence of his dialectics, mere tradition, no matter how venerable, whether political, religious, or philosophical, found no quarter with William of Occam. "The invincible Doctor," as he soon proved himself, threw the weight of his influence, as the advocate of Nominalism and free opinion, and the sworn foe of Realism and intellectual submission, on the side of Philip the Fair of France in his contest with Pope Boniface VIII. William published a celebrated manifesto in favour of the cause, entitled Disputatio super potestate ecclesiasticae prelatis atque principibus terrarum commissa, which the successor of St Peter did not at all relish. The author and his followers were branded as innovators in the church as well as in the schools; and Nominalism became with the ecclesiastical party another name for heresy. On the death of Boniface, Pope John XXII. summoned Occam and his disciples before him at Avignon, and the "invincible Doctor" only escaped the vengeance of his Holiness by a precipitate flight to Bavaria, on the 26th of May 1328. Here he gained the protection of Louis, and remained till his death, which took place at Munich some twenty years afterwards. (For the doctrines of Occam, see Nominalism and Realism.)

The following writings compose Occam's philosophical works—Super librum Sententiarum subtantiae questiones, fol., Lyon, 1485, in which will be found the substance of the author's metaphysical doctrines; Quodlibeta system, fol., Paris, 1487, and Strasburg, 1491; Summa logicae, 4to, Venezia, 1593, and frequently reprinted; Major summa logicae, 4to, Venezia, 1592; Questiones in libros Physicorum, fol., Strasbourg, 1491, 1506; Explicatio quaestiorum super totam artem artis extrema, videlicet in Porphyrii predicabilibus et Aristotelii praedicamentis, fol., Bologna, 1496.