His principal work is the commentary on the Sentences. This survives in three forms: copies of his own lecture notes (Lectura) for the Oxford commentary; copies of students’ notes (Reportatae) taken from the various lectures; copies of his own final revision of the various notes. This last and most important version (the Ordinatio) was left incomplete at his death. His other writings include commentaries on some of *Aristotle’s and *Porphyry’s works on logic, a set of quaestiones on Aristotle’s Metaphysics, a Tractatus de Primo Principio, and *Quodlibeta.
Writing after the condemnation of a number of Aristotelian positions (including some opinions of St *Thomas Aquinas) by the Abp. of Paris in 1277, Scotus attempts to mediate between Aristotelianism and the Augustinianism associated with his main opponent, *Henry of Ghent. Scotus definitively rejects the Aristotelian principle of plenitude (no genuine possibility can remain forever unrealized), and posits instead the radical contingency (non-necessity) both of created entities and of God’s action. He believes that for human will to be genuinely free, it must be really able to will what it does not in fact choose to will. The intellect offers a strong guidance to the will, inclining it to the right act; but the will is able to go against the suggestion of reason. Thus, Scotus denies the universal applicability of Aristotle’s principle, ‘everything which is moved is moved by some other agent’, on the grounds that the will is freely capable of moving itself to an action. God’s will is free in the sense that God can freely desire opposite objects and effects: thus, human actions are given moral value only if God commands them. The exception is the act of loving God. It is impossible to understand the word ‘God’ without also understanding that God should be loved. For this reason, God cannot will that creatures hate Him.
Scotus’ proof of the existence of God attempts to show that one necessary cause is required in order to explain the existence of contingent entities. Creatures do not exist necessarily, and have essentially only the possibility of existence. But if the existence of some creature is really possible, then the creature must be capable of being caused; and if a creature is capable of being caused, there must be some agent able to cause it. Thus, in order to explain the existence of creatures, it is necessary to posit some being that exists necessarily.
Scotus rejects St Thomas Aquinas’s position that individuation is by matter, and holds instead that the unity and individuality of each created thing is given by its own form of individuality (haecceitas) added to its matter and form. Unlike some of his contemporaries, he does not think that all substances—including God and the *angels—are material. He also believes that not every complete individual thing is a person: Christ’s human nature is a complete individual thing that is not a human person. Individuals are properly called persons by virtue of the negative qualification of not being united to a divine person. Scotus rejects the Aristotelian position that the intellect can know only the universal ideas that it abstracts from sense data, and allows instead a certain intuitive knowledge of individual things. On the other hand, he rejects Henry of Ghent’s Augustinian position that certitude follows only from divine illumination, and holds, like Aquinas, that certitude derives from necessary principles that are known naturally by the intellect.
In his theology Scotus lays stress on the primacy of Christ as the supreme manifestation of God’s love; it follows that Christ’s coming was not conditioned by any other historical events, and in particular that the Incarnation would have taken place irrespective of the *Fall. For Scotus this also entailed the doctrine of the *Immaculate Conception of the BVM, a doctrine that he was the first well-known theologian to defend.
F. L. Cross and Elizabeth A. Livingstone, The Oxford Dictionary of the Christian Church, 3rd ed. rev., 516 (Oxford; New York: Oxford University Press, 2005).