Robert Grosseteste and Roger Bacon

The newly translated Greek and Arabic treatises had an immediate effect on the University of Oxford. Its first chancellor, Robert Grosseteste (c. 1175–1253), commented on some of Aristotle’s works and translated the Nicomachean Ethics from Greek to Latin. He was deeply interested in scientific method, which he described as both inductive and deductive. By the observation of individual events in nature, human beings advance to a general law, called a “universal experimental principle,” which accounts for these events. Experimentation either verifies or falsifies a theory by testing its empirical consequences. For Grosseteste, the study of nature is impossible without mathematics. He cultivated the science of optics (perspectiva), which measures the behaviour of light by mathematical means. His studies of the rainbow and comets employ both observation and mathematics. His treatise De luce (1215–20; On Light) presents light as the basic form of all things and God as the primal, uncreated light.

Grosseteste’s pupil Roger Bacon (c. 1220–92) made the mathematical and experimental methods the key to natural science. The term experimental science was popularized in the West through his writings. For him, human beings acquire knowledge through reasoning and experience, but without the latter there can be no certitude. Humans gain experience through the senses and also through an interior divine illumination that culminates in mystical experience. Bacon was critical of the methods of Parisian theologians such as St. Albertus Magnus (c. 1200–80) and Aquinas. He strove to create a universal wisdom embracing all the sciences and organized by theology. He also proposed the formation of a single worldwide society, or “Christian republic,” that would unite all humankind under the leadership of the pope.

William of Auvergne

At the University of Paris, William of Auvergne (c. 1180–1249) was one of the first to feel the impact of the philosophies of Aristotle and Avicenna. As a teacher and then as bishop of Paris, he was concerned with the threat to the Christian faith posed by pagan and Islamic thought. He opposed the Aristotelian doctrine of the eternity of the world as contrary to the Christian notion of creation. His critique of Avicenna emphasized the latter’s conception of God and creation. Against the God of Avicenna, who creates the universe eternally and necessarily through the mediation of 10 intelligences, William defended the Christian notion of a God who creates the world freely and directly. Creatures are radically contingent and dependent on God’s creative will. Unlike God, they do not exist necessarily; indeed, their existence is distinct from their essence and accidental to it. God has no essence distinct from his existence; he is pure existence. In stressing the essential instability and temporality of the world, William attributed true existence and causality to God alone. Although a follower of Augustine, William, like others of his time, was compelled to rethink the older Augustinian notions in terms of the newer Aristotelian and Avicennian philosophies.

Bonaventure

The Franciscan friar St. Bonaventure (c. 1217–74) reacted similarly to the growing popularity of Aristotle and his Arabic commentators. He admired Aristotle as a natural scientist, but he preferred Plato and Plotinus, and above all Augustine, as metaphysicians. His main criticism of Aristotle and his followers was that they denied the existence of divine ideas. As a result, Aristotle was ignorant of exemplarism (God’s creation of the world according to ideas in his mind) and also of divine providence and government of the world. This involved Aristotle in a threefold blindness: he taught that the world is eternal, that all men share one agent intellect (the active principle of understanding), and that there are no rewards or punishments after death. Plato and Plotinus avoided these mistakes, but because they lacked Christian faith, they could not see the whole truth. For Bonaventure, faith alone enables one to avoid error in these important matters.

Bonaventure did not confuse philosophy with theology. Philosophy is knowledge of the things of nature and the soul that is innate in human beings or acquired through their own efforts, whereas theology is knowledge of heavenly things that is based on faith and divine revelation. Bonaventure, however, rejected the practical separation of philosophy from theology. Philosophy needs the guidance of faith; far from being self-sufficient, it is but a stage in a progression toward the higher knowledge that culminates in the vision of God.

For Bonaventure, every creature to some degree bears the mark of its Creator. The soul has been made in the very image of God. Thus, the universe is like a book in which the triune God is revealed. His Itinerarium mentis in Deum (1259; The Soul’s Journey into God) follows Augustine’s path to God, from the external world to the interior world of the mind and then beyond the mind from the temporal to the eternal. Throughout this journey, human beings are aided by a moral and intellectual divine illumination. The mind has been created with an innate idea of God so that, as Anselm pointed out, humans cannot think that God does not exist. In a terse reformulation of the Anselmian argument for God’s existence, Bonaventure states that if God is God, he exists.

Albertus Magnus

The achievement of the Dominican friar Albertus Magnus was of vital importance for the development of medieval philosophy. A person of immense erudition and intellectual curiosity, he was one of the first to recognize the true value of the newly translated Greco-Arabic scientific and philosophical literature. Everything he considered valuable in it he included in his encyclopaedic writings. He set out to teach this literature to his contemporaries and in particular to make the philosophy of Aristotle, whom he considered to be the greatest philosopher, understandable to them. He also proposed to write original works in order to complete what was lacking in the Aristotelian system. In no small measure, the triumph of Aristotelianism in the 13th century can be attributed to him.

Albertus’s observations and discoveries in the natural sciences advanced botany, zoology, and mineralogy. In philosophy he was less original and creative than his famous pupil Aquinas. Albertus produced a synthesis of Aristotelianism and Neoplatonism, blending together the philosophies of Aristotle, Avicenna, and Ibn Gabirol and, among Christians, Augustine and Pseudo-Dionysius.