Metaphysics: Ancient and Medieval

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Metaphysics: Ancient and Medieval

In the early twenty-first century metaphysics is a term used fairly loosely to describe philosophical investigation of the fundamental constituents of reality. But, in the Middle Ages, there was great debate about what was the subject of metaphysics, and that controversy had ancient roots.

What Is Metaphysics?

The word metaphysics is taken from the title, given by an editor in antiquity, to a treatise (or, rather, a set of material, not all of which belongs together) by Aristotle (384322 b.c.e.): the word may have been chosen just because the work was placed after (meta ) the physics, or it may have meant that the work deals with things beyond the physical. Aristotle does, in most of the Metaphysics, seem to believe that he is engaged in a single, distinctive enterprise of "first philosophy"but he characterizes its aim in a number of different, and arguably incompatible, ways: it is the study of first principles, or of being qua being, or the investigation of substance, or its main concern is with immovable substances, that is to say, with the gods. This final, theological aspect led many later ancient philosophers to envisage the Metaphysics as an investigation, not of being in general, but of the highest sort of supra-sensible beingan approach that fitted the overwhelming concern of late antique philosophers with the intelligible world and the general wish to syncretize Aristotle and Plato.

In the Middle Ages, the question of the subject-matter of metaphysics became more problematic. The two greatest medieval Islamic philosophers, Avicenna (Ibn Sina; 9801037) and Averroës (Ibn Rushd; 11261198), knew Aristotle's Metaphysics well. Avicenna held that God could not be the subject of metaphysics, because it is in metaphysics that the existence of God is demonstrated, and no science can demonstrate the existence of its own subject. Metaphysics, therefore, has as its subject being qua being. Averroës disagreed. He held that the existence of God is demonstrated in physics, and so metaphysics can be regarded as the study of the first being, the separate substance that, as final cause, is the mover of all things.

Avicenna's view predominated among the Christian Scholastics, who saw metaphysics primarily as the study of being in general (ens commune ) rather than of a particular, special being. But Duns Scotus (c. 12661308), at least, was willing to say that God is a sort of being, and so is considered in metaphysics along with all other beings. Thomas Aquinas's (c. 12241274) position had been, perhaps, more nuanced. God is not, he thought, contained under the notion of being in general, but he is included within metaphysics in that he is the cause of being in general, which the subject studies.

Form in Metaphysics

One central notion in metaphysics (understood in a broad sense, and going back to before the word was invented) is that of form. Plato (c. 428348/7 b.c.e.) reasoned that there could be no knowledge of the objects of everyday experience, but merely opinion about them, because they are constantly changing and cannot be said to be, but merely to become. The objects of knowledge, he thought, must be unchanging thingswhat he called "Forms" or "Ideas." Although Platonic Forms can be grasped only through the powers of the intellect, not by the senses, they are by no means merely mental entities, but independently existing realities, as a result of participation in which the objects of sense perception have the characteristics they doso, for example, beautiful things are beautiful by virtue of participating in the Form of Beauty (or, as Plato sometimes says, in Beauty Itself). Beyond this, Plato gives rather different accounts of the Forms from dialogue to dialogue, and even within the same dialogue. In perhaps his most famous discussion of them, in the central books of the Republic, he presents a supreme Form, the Form of the Good, which is understood only after years of intellectual training. The other Forms, Plato says, depend on the Form of the Good and are grasped properly only once the Form of the Good is grasped. In the Timaeus, Plato shows the universe being constructed as an ensouled living thing, according to the pattern of the Ideas.

Aristotle's account in his Metaphysics of how things are constituted also uses the notion of Form, but it is treated very differently. The Forms Aristotle discusses are those of types of natural things, divided according to natural kinds. For instance, one natural kind is Man, another is Horse. According to this hylomorphic account, each man is a man by virtue of the Form of humanity, and each horse a horse by virtue of the Form of equinity. These Aristotelian Forms are not, like Plato's Forms, independent single entities in which many particular sensible things participate. Rather, a particular member of a natural kindthis man, for instanceis a concrete whole composed of matter and Form. Yet the Form that makes him a man is the same as the Form by which any other man is a man. By grasping this Form with our intellects, we have a universal notion of Man, which we are able to use in formulating scientific truths, not about this or that man, but about Man in general.

In the Middle Ages, Plato's Theory of Forms in its pure state had very few adherents. But an adapted version of it, which goes back to Philo (c. 13 b.c.e.45/50 c.e.), the Hellenistic Jewish thinker, was extremely popular: the Forms are said to be in the mind of God. Thinkers as diverse as Augustine, Eriugena, Abelard, and Aquinas used this idea as one of the ways of describing God's relation to created things. It was not until William of Ockham (c. 1285?1349), in the early fourteenth century, that this picture was seriously questioned. Adoption of this version of Platonic Ideas still left Aristotelian hylomorphism as the main way of explaining the constitution of concrete things, and there was a vigorous debate in the twelfth century about whether (on the basis of the version of Aristotle's theory proposed in his Categories ) Forms in reality are really universal, or are universal merely in the way they are used in human thought and language. In the thirteenth and fourteenth centuries, hylomorphism was the basis (following Aristotle's On the Soul ) for the theory of intellectual cognition. The Form that makes, for example, a horse a horse informs the matter-like potential intellect of the person who intellectually grasps the notion of horse.

Two Main Questions of Medieval Metaphysics

Another important debate in later medieval metaphysics was about whether essencethe sort of thing something isand existence (esse ) the fact of the thing's actually existingare really distinct. Aquinas held that they are, and that in everything except God there is a real composition between them. This theory allows Aquinas, who does not believe that every creature is a composite of matter and form, to identify one sense in which nevertheless God alone is noncomposite. Not many of his successors followed him, however, in this insistence that the distinction between essence and existence is real. Some, such as Duns Scotus, held the distinction to be more than mental, but less than real, while Ockham argues that "essence" and esse mean the same thing.

The same thinkers also considered whether "being" in a general sense is a notion under which fall both God and his creatures. Aquinas insisted that the notion applies only analogically (and so equivocally) to God, on the one hand, and created things on the other. Scotus (followed by many fourteenth-century thinkers) argued for a subtle form of univocal predication of "being," although he fully acknowledged that God's infinite way of being is unlike that of any creature.

See also Aristotelianism ; Form, Metaphysical, in Ancient and Medieval Thought ; Metaphysics: Renaissance to the Present .



Aristotle. Metaphysics. In The Complete Works of Aristotle, edited by Jonathan Barnes. Vol. 2. Princeton, N.J.: Princeton University Press, 1985. Translations with extensive philosophical annotation of individual books of the Metaphysics can be found in the Clarendon Aristotle Series, published by Oxford University Press.

Plato. Dialogues. Various translations are available.

Aquinas, Thomas. Selected Philosophical Writings. Edited and translated by Timothy McDermott. Oxford and New York: Oxford University Press, 1993. Contains a number of passages central to Aquinas's metaphysics, including the whole of De ente et essentia, 90113.


Barnes, Jonathan. "Metaphysics." In The Cambridge Companion to Aristotle, edited by Jonathan Barnes, 66108. Cambridge, U.K., and New York: Cambridge University Press, 1995.

Dumont, S. "Henry of Ghent and Duns Scotus." In The Routledge History of Philosophy, Vol. 3: Medieval Philosophy, edited by John Marenbon, 291328. London and New York: Routledge, 1998. The chapter is almost entirely on their metaphysics.

White, Nicholas P. "Plato's Metaphysical Epistemology." In The Cambridge Companion to Plato, edited by Richard Kraut, 277310. Cambridge, U.K.: Cambridge University Press, 1992.

Wippel, John F. "Essence and Existence." In Cambridge History of Later Medieval Philosophy: From the Rediscovery of Aristotle to the Disintegration of Scholasticism, 11001600, edited by Norman Kretzmann, Anthony Kenny, and Jan Pinborg, 385410. Cambridge, U.K., and New York: Cambridge University Press, 1982.

John Marenbon