Joseph Caspi (1297–1340), a prolific philosopher and exegetical commentator, maintained a somewhat unsystematic philosophical position that seems to have been influenced by Averroës. He expressed the opinion that knowledge of the future, including that possessed by God himself, is probabilistic in nature. The prescience of the Prophets is the same. Caspi’s interest in this problem may well have had some connection with the debate about future contingencies in which Christian Scholastics were engaged at that time.
Moses of Narbonne, or Moses Narboni, like many other Jewish scholars of the 14th century, wrote mainly commentaries, including those on biblical books, on treatises of Averroës, and on Maimonides’ Guide. In his commentary on the Guide, Narboni often interprets the earlier philosopher’s opinions by recourse to Averroës’ views. Narboni also expounded and gave radical interpretations to certain conceptions that he understood as implied in the Guide. According to Narboni, God participates in all things, because he is the measure of all substances. God’s existence appears to be bound up with that of the world, to which he has a relation analogous to that between a soul and its body (a comparison already made in the Guide). Gersonides
Gersonides, also known as Levi ben Gershom (1288–1344), wrote the systematic philosophical work Sefer milḥamot Adonai (“The Book of the Wars of the Lord”), as well as many philosophical commentaries. Gersonides cited Greek, Arabic, and Jewish thinkers, and in many ways his system appears to have stemmed from the doctrines of Maimonides or Averroës, regardless of whether he agreed with them. For example, he explicitly rejected Maimonides’ doctrine of negative theology. Although he never explicitly mentioned Christian Scholastic philosophers, a comparison of his opinions and of the particular problems that engaged his attention with the Scholastic writings of his period suggests that he was influenced by the Latins on certain points.
Gersonides disagreed both with the Aristotelian philosophers who maintained the eternity of the world and with the religious partisans who believed in the creation of the world in time out of nothing. He argued instead that God created the world in time out of a preexistent body that lacked all form. As Gersonides conceived it, this body seems to be similar to primal matter.
The problem of human freedom of action and a particular version of the problem of God’s knowledge of future contingencies form an important part of Gersonides’ doctrine. Unlike the great Jewish and Muslim Aristotelians, Gersonides believed in astrology and held that all happenings in the world except human actions are governed by a strict determinism. God’s knowledge does not extend to individual human acts but embraces the general order of things; it grasps the laws of universal determinism but is incapable of apprehending events resulting from human freedom. Thus, the object of God’s knowledge is a totally determined world order, which differs from the real world insofar as the latter is in some measure formed according to human freedom.
Gersonides does not appear to have assigned to the prophets any political function; according to him, their role consists of predicting future events. The providence exercised by the heavenly bodies ensures the existence in a given political society of people with an aptitude for the handicrafts and professions necessary for the survival of the community. He remarked that in this way the various human activities are distributed in a manner superior to that outlined in the Republic of Plato. Thus, he explicitly rejected Plato’s political philosophy, which, because it was suitable to a society ruled through laws promulgated by a prophet (Muhammad), had been an important element of Jewish philosophy in the Arabic period. Ḥasdai Crescas
The Spanish Jewish thinker Ḥasdai ben Abraham Crescas (1340–1410), like Gersonides, had thorough knowledge of Jewish philosophy and partial knowledge of Islamic philosophy; in both areas he seems to have been influenced by Christian Scholastic thought. Moreover, in certain important respects Crescas was influenced by Gersonides himself. One of Crescas’s main works, Or Adonai (“The Light of the Lord”), was quite contrary to Gersonides in its attempt to expose the weaknesses of Aristotelian philosophy. This attitude may be placed in the wider context of the return to religion itself, as opposed to the Aristotelian rationalization of religion, and the vogue of Kabbala (esoteric Jewish mysticism), both of which were characteristic features of Spanish Jewry in Crescas’s time. This change in attitude may have been a reaction to the increasing precariousness of the position of the Jewish community in Spain.
The criticism of the extreme rationalism of some medieval Aristotelians coincided historically with a certain disintegration of and disaffection toward classical Aristotelian Scholasticism. This trend was associated with the so-called voluntarism of John Duns Scotus (c. 1266–1308), the nominalism of William of Ockham (c. 1285–1347/49) and other 13th–14th-century Christian Scholastics, and the development of anti-Aristotelian physics at the University of Paris and elsewhere beginning in the 14th century. Significantly, there is a pronounced resemblance between Crescas’s views and two of these trends, Scotism (the teachings of Duns Scotus and his followers) and the “new” physics.
Crescas accepted Gersonides’ view that divine attributes cannot be negative, but unlike his predecessor his explanation of the difference between the attributes of God and those of created beings centred on the contrast between an infinite being and finite beings. It is through infinitude that God’s essential attributes—wisdom, for instance—differ from the corresponding and otherwise similar attributes found in created beings. In Crescas’s doctrine, as in that of Spinoza, God’s attributes are infinite in number. The central place assigned to the doctrine of God’s infinity in Crescas’s system suggests the influence of Duns Scotus’s theology, which is similarly founded upon the concept of divine infinity.
The problem of the infinite was approached from an altogether different perspective in Crescas’s critique of Maimonides’ 25 propositions, which Maimonides had set forth in the Guide as the basis of his proof of the existence of God. Crescas’s purpose in criticizing and rejecting several of these propositions was to show that the traditional Aristotelian proofs (founded in the first place on physical doctrines) were not valid. In his critique, Crescas attempted to disprove the Aristotelian thesis that the existence of an actual infinite is impossible. He held that space is not a limit but a three-dimensional extension, that it is infinite, and that, contrary to Aristotle, the existence of a vacuum and of more worlds than one is possible. He also argued that the thesis of the Aristotelian philosophers that there exists an infinite number of causes and effects, which have order and gradation, was impossible. This thesis refers not to a temporal succession of causes and effects that have a similar ontological status but to a vertical series, descending from God to the lowest rung in creation. His attacks were likewise directed against the Aristotelians’ conceptions of time and matter.
Crescas’s fundamental opposition to Aristotelianism is perhaps most evident in his rejection of the conception of intellectual activity as the supreme state of being for humans and for God. Crescas’s God is not first and foremost an intellect, and humanity’s supreme goal is not to think but to love God with a love corresponding, as far as possible, to his infinite greatness and to rejoice in the observance of his commandments. God too loves human beings, and his love, in spite of the lowliness of its object, is proportionate to his infinity.