Medieval Philosophy

by Peter S. Adamson

If the whole of society is like a single organism, then each of its parts is intended to contribute to the welfare of the whole. Echoing themes already found in Plato’s Republic, John insists that each member of the society must carry out his proper function if the society is to flourish (§6.22). This applies even, or rather especially, to the ruler. John recognizes the unchallenged authority of the ruler, who is an image of God upon earth (§4.1). But this does not mean that the ruler is somehow outside of the social body as a whole. Rather, as its head, the true king or “prince” is one who looks to the good of all the members, and he is subject to the laws just like anyone else (§4.1, 8.17). Again as in Plato, the benevolent ruler has a kind of perverse twin, the malevolent tyrant, who instead uses his position for selfish gain: an image of Satan, rather than of God. John’s political theory takes a startling turn when he expresses approval of tyrannicide, that is, the murder of such an evil king.13 He arrives at the topic in a rather roundabout way, in the course of talking about flattery at court. Such behavior is normally condemnable, but flattery of a tyrant may be excused as a necessary expedient. John then adds that we’re surely allowed to flatter such a ruler, given that we’re even permitted to slay him (§3.15). After dropping this bombshell, John says little more on the topic. He does later mention a series of classical tyrants who got their comeuppance, sometimes ...

But like Manegold of Lautenbach, John thinks that moral failure can undermine a secular ruler’s legitimacy, whereas this is never the case with a pope. Here John taps into a rich vein of political thought, which holds that an unjust ruler is not just an unfortunate cross to be borne, but in truth no ruler at all, whether or not anyone is in a position to do something about it. (Remember the etymology provided by Isidore of Seville, who related the Latin word for king, rex, to the word recte, meaning “correctly” or “with justice”; see Chapter 2 above.) With his focus on justice and his insistence that even the king is subject to the law, John was a man of his time. The twelfth century was not just an era of resurgent philosophy. It was also a time of law, with legal scholars doing what John was doing: turning back to antiquity for inspiration, and adapting classical ideas for their new situation.

We may immediately feel wrong-footed, though. The phrase “natural law” conjures up the idea of a set of rules that we should all be able to access with our inborn reason. Gratian seems to agree, since he will go on to say that

natural law emerges along with “rational creatures” and never changes thereafter (§5). But if natural law has to do with reason, and not revelation, then why draw such a strong link between natural law and Scripture? Of course, Gratian is writing about church law, so he wants to stress that Scripture does indeed have a distinctively legal kind of authority. But he does not seem to be saying that the deliverances of natural law can only be reached by turning to Scripture. Nor does he think that everything found in Scripture is part of the natural law (§6). Rather, he’s doing what he does best, by emphasizing agreement, in this case between natural and religious law. His example is well chosen. The golden rule may be found in the New Testament, but it is also something that humans could grasp without the benefit of revelation. Even then, God would be part of the story. After all, human reason itself is a divine gift, as far as Gratian is concerned. Thus, heathens too are drawing on a heavenly source when they discover and follow the natural law with no help from the Bible. Alongside the natural law, there is what Gratian calls “human law” (§1, quoting Isidore of Seville). This means any law set down by a human authority, whether secular or ecclesiastical. In addition, there are all the requirements and guidelines that fall under the heading of “custom.” How, then, does custom relate to human and natural law?5 One thing is clear: no human law or custom has force if it contrav...

He reasonably points out that laws are pointless if they contradict deeply ingrained social practices

Gratian also offers influential remarks on another issue: the question of when Christians can justly partake in war (see further Chapter 40).6 He sets down two basic requirements here, namely that the war be declared by a legitimate authority and that the war be undertaken for reasons of defense or redressing an injury, and for the sake of justice rather than revenge.

Since the soul seems to be much more like God than the body is, it may seem natural to assume that Christ’s divine nature had to do especially with his soul. And indeed, Peter Lombard remarks that divinity became united to Christ’s flesh “through his intellect” or rational soul (§2.2.1). On the other hand, Christ’s divinity should be somehow joined to his entire human nature, and human nature does include the body. How then was divinity joined to both body and soul in Christ?

The first answer, inspired by Hugh of Saint Victor, is that the body and soul were both “assumed” by the divine nature (§6.2.1). This avoids the difficulty of leaving Christ’s body outside his divinity, but threatens to eliminate the human nature entirely. The second view, which is that of Gilbert of Poitiers, takes more or less the opposite approach by saying that divinity is a third, distinct thing in Christ added to body and soul (§6.3.1). Here there’s no danger of eliding Christ’s humanity, but it’s difficult to see how Christ will be a single, unified person; divinity and humanity would be juxtaposed rather than fused. Indeed, you might even wonder how on this view we have one rather than two persons in Christ, and the whole point was to understand how a single person can have two natures. Finally, there is the third view, based on Abelard. This time the idea is to start with the divine Person, and imagine it taking on human nature in a more accidental or extrinsic way, like someone putting on a set of clothes that he can later take off (§6.4.1).

Indeed, the debate over the Incarnation we’ve just been discussing has a variety of philosophical implications. Any solution depends on a theory of human nature, and a view on the question of how natures or essences belong to particular things; it connects to questions about parts and wholes too.

Such details of vocabulary are glimpses of a wider process. As Greek and Arabic works became available to the medieval Latin reader, philosophy itself was revolutionized. This was one of the two historical developments that had the greatest impact on medieval philosophy as we move forward into the thirteenth century;

The influx of works by Aristotle, Averroes, Avicenna, and others led to a new understanding of what philosophy is in the first place.

The resulting changes were profound. Even a very well-informed twelfth-century thinker like John of Salisbury could proclaim solidarity with the

moderate skepticism of Cicero, according to which we must often content ourselves with merely probable beliefs.17 That favorite text of the twelfth century, Plato’s Timaeus, fit nicely with this approach since its cosmology is presented as a mere “likely account” of the universe. The average thirteenth-century scholastic will be having none of this. He has read the Posterior Analytics and knows that philosophy is meant to consist of valid syllogistic arguments grounded ultimately in certain first principles. Aquinas (admittedly, not exactly an average scholastic thinker) will even claim that theology is a special case of an Aristotelian demonstrative science.

Yet the fact that we still use the word “university” can be misleading. Originally, universitas just meant a group of people who banded together for collective action.

One might take the emergence of the universities as a clear victory for Team Abelard. But in fact, they sought to preserve the moral framework of monastic life alongside

the liberal arts curriculum. Such moral traits as discipline and modesty were considered as important for the student as the knowledge they would acquire.

Another difference between the universities and the earlier schools was simply the higher degree of organization implied by the term universitas.

This is another important contrast between medieval universities and the ones we know: these great centers of learning were to a large extent offering what we would think of as a high school education.

But what about Aristotle’s works on natural philosophy and his Metaphysics? These were full of problematic teachings. Among other things Aristotle seemed to depict the human as a mortal being whose soul was a mere form of the body, suggesting that an afterlife is impossible, and also to argue that the universe had always existed rather than having been created.

In the first half of the thirteenth century, progress was made especially in understanding individual terms. For this reason, the logicians of this period are credited with devising what is called “terminist” logic.

His theory of dicta (“things that can be said”) played a role in his nominalist position on universals, but it was more basically a point of logic. A dictum such as “Hiawatha’s being a giraffe” does not yet assert that Hiawatha actually is a giraffe. To do that, you must deploy the verb “is,” or in Latin est: “Hiawatha is a giraffe,” or if you prefer, Hiawatha camelopardus est. Logicians then, as now, called this verb a “copula.” One thing we can see from this example is that not all the terms in such a proposition are “categorical,” that is, standing for a subject or predicate. Rather, we must add another kind of term, a copula, in order to have an assertion at all.

Alongside “categorematic” terms that refer to the subject and predicate of the proposition, they recognized “syncategorematic” terms, adding the prefix syn-, which means “with” in Greek. This vocabulary was actually borrowed from grammar, showing yet again the interplay of the three arts of the trivium. Much of the technical discussion in terminist logic involved syncategorematic terms. Take, for instance, the so-called “modal” terms “necessarily” and “possibly.”8 If I say

“Giraffe is necessarily animal,” is “necessarily” functioning as an adverb that modifies the whole proposition? Or does it only modify the predicate, so that I am ascribing to giraffe the property “necessarily-an-animal”? That might seem like a pointless question, but it is actually crucial. If “necessarily” is attached to the predicate and not the copula, then the proposition as a whole is being asserted as merely true, and not as a necessary truth. In which case I won’t be able to use this premise in an argument to prove other necessary truths, because you can’t infer a necessary truth from a mere truth. In this case, the terminists held that the necessity does apply to the whole proposition. It’s perhaps not surprising that a word like “necessarily” would give rise to such difficulties. But the terminists found that even the copula needed careful thought. Bill Clinton was right: it isn’t so obvious what the meaning of the word “is,” is. If I say “Giraffe is animal,” does that refer to some one existing giraffe like Hiawatha, who is an animal? Does it mean that all the presently existing giraffes are animals? Does it mean that all past, present, and future giraffes are animals? Or perhaps even that there is a conceptual connection between “giraffe” and “animal,” such that my claim would be true even if there are never any giraffes?

They called its general meaning its “signification.”10 Following suggestive remarks in Aristotle, signification was defined with reference to communication between a speaker and a listener. The signification of the term “giraffe” is either the concept in my mind that I’m trying to convey to you when I say “giraffe” or the concept that arises in your mind when you hear me say it.11 The concepts in our minds in turn signify things out in the world, for instance Hiawatha in the giraffe enclosure. Yet as we’ve just seen, I don’t need to have any particular giraffe in mind when I say “Giraffe is animal.” So the terminists devised a theory about what they called “supposition.”12 A term “supposits” for whatever it stands for in a given proposition. So the term “giraffe” has only one signification, but many possible suppositions.

Most generally, the terminists recognized three types, which were called personal, simple, and material supposition. Personal supposition is when a term supposits for a thing or things in the world.

But what if I am not referring to any giraffes in particular, but just to the basic concept of “giraffe”? In that case, I am using what the terminists called “simple” supposition. William of Sherwood’s example is “Human is a species.” Obviously, this isn’t a case of personal supposition at all, since it isn’t as if Bill Clinton or any other human is a species. In addition to personal and simple supposition, the third and final type is illustrated by propositions like “Human has five letters.” Here I am referring neither to particular humans nor to the species human, but to the word itself. The terminists express this by saying that I am employing neither personal nor simple supposition, but “material” supposition. Nowadays we could simply make this distinction using quotation marks: a human doesn’t have five letters, but “human” does. What is the point of all this? Most basically, the terminists were trying to keep track of what we are and are not committing ourselves to when we say things. Among other things, this enables us to avoid making fallacious inferences. As they again spared no ingenuity in pointing out, many fallacies are invalid because they use the same term twice, but with two different kinds of supposition.

Supposition theory wasn’t only a tool for avoiding mistakes. It also provided a context for arguing over numerous important philosophical issues. Notably, we can now recast the problem of universals as one about the supposition of terms. If I say “Red is a color,” what is the term “red” suppositing for, and why is my statement true? It is tempting to say that “red” here has simple supposition and thus refers to the universal red; the reason it is true is that the universal red is a real thing, and is a color. Of course, this interpretation would be unacceptable to those thinkers who, in the tradition of Abelard, insisted that nothing real can be universal. Thus, in the fourteenth century, the nominalist John Buridan is going to argue against distinguishing simple and

material supposition. Since the universal is actually just a name, saying something like “Human is a species” or “Red is a color” is actually a statement about the word “human” or the word “red.”15 The work of the terminists also raised problems that belong to what we would nowadays call philosophy of language.

Adding syncategorematic terms can change the supposition of the term. Suppose I take the proposition “Giraffes are tall” and add the word “always,” to get “Giraffes are always tall.” I thereby extend the scope of (or as the medievals said, “ampliate”) the term “giraffes,” so that it supposits for the giraffes that exist in the past and future, and not just for the ones that exist now. Conversely, if I add the word “blue” and say “Blue giraffes are tall,” I “restrict” the term “giraffes” to only those giraffes that are blue. The reason this is exciting is that it suggests a general theory about language: what determines the supposition of a term is its context. This suggestion was debated in the thirteenth century. Some logicians, especially in Oxford, thought that supposition was indeed always a function of context. Others, especially in Paris, held that each term has a “natural” supposition all by itself, which can be altered by its context to produce what they called “accidental” supposition.

The Stoics had not added much to Aristotle’s pioneering work on categorical syllogisms, but had explored other kinds of inferences, including those involving “if-then” statements.17 Just like the late ancient Aristotelians, the medieval logicians were loath to admit that Aristotle had dropped the ball when it came to these inferences. Instead, they tried to show how Aristotelian logic could be extended to handle them, thinking of an “if-then” statement as a “molecular” proposition made up of two “atomic” statements, both of which are predications. When I say, “If Hiawatha is a giraffe, then she is tall,” the “if” and “then” simply link two predications: “Hiawatha is a giraffe” and “Hiawatha is tall.”

So far, we’ve been talking about the physical mechanics of motion. But if you think about it, motion is also rather perplexing from a metaphysical point of view. This is because it seems to exist only over time, rather than at a time. At any moment during the time the baseball is getting cozy and warm by the fire, it only ever has one given temperature. And at any instant while a thrown baseball is hurtling through the air, it only has one position. How are these temperatures and positions glued together, as it were, into a single, fluid change or motion? The question was raised by the Pre-Socratic thinker Zeno of Elea, a follower of Parmenides.5 He argued that an arrow in flight is not moving because it is at rest at each time during its supposed flight. This was another puzzle that engaged the attention of medieval commentators. They looked at it from a typically

Aristotelian point of view, by asking how motion relates to the scheme of ten categories. But we can think about the problem from a less technical perspective, by simply asking how motion or change relates to the property that will be reached by the end of the motion or change.

Averroes took this to mean that a motion in respect of a quality, for instance, is nothing more than that quality in an incomplete state. For instance, when the baseball is being warmed up, it is on the way to being hot, so we can just think of its status at any one time as incomplete hotness. In other words, the change involved in heating is nothing more than a series of stages of heat.7

One of these commentators complains that Averroes’ idea of motion as an incomplete property is itself incomplete. Each stage in the motion or change, for instance each degree of heat in the increasingly warm baseball, is a product of change just as much as the degree of heat achieved at the end of the heating process. This means we’ll need a separate motion to explain each partial change along the way. Besides, the commentator adds, some changes aren’t gradual. When a substance like an animal comes to be, it does so “all at once” and not part by part. Despite these criticisms, a theory of motion inspired by Averroes is going to be put forward by another commentator on Aristotle in the following decades, whose name is not only known but renowned: Albert the Great. He proposes that we can think of a change as being just the same form as the one that will exist at the end of the change, but with potentiality mixed in. Across time, the change “flows” towards its final result, with the form becoming progressively more actual at each moment.

The doubt is similar to the one we saw concerning motion. Just as a motion unfolds across time and so is never entirely present, so does temporal duration seem to lie outside what presently exists. After all, the past is already gone, the future is yet to come, and the present moment has no duration of any magnitude but is an undivided instant. We often compare temporal duration to spatial magnitude, talking about a “long” or “short” time the way we might talk about a long or short distance. But actually space is very different from time: the distance between pitcher’s mound and home plate is all present at once, whereas the time it takes the ball to travel that distance is not.

The standard Aristotelian view here is that nothing can be actually infinite, but there can be potential infinities. For instance, you cannot have an infinitely big body, but you could have a body that is increasing indefinitely in size while always remaining finitely large.

At the bottom of this dispute is an ambiguity in the concept of infinity. Is infinity an unlimited magnitude? Or is it just the notion of being indefinite, as when you can at each stage make an even smaller division than the last division you made?

For Aristotle, there is nothing outside the spherical cosmos, not even empty space. So there is no further body containing the cosmos, to provide it with a place. Absurdly, it would seem that the universe is nowhere at all.

As for the place of more everyday objects like baseballs, they suggest that we might be able to find a compromise between Aristotle’s definition and the idea that place is extension. After all, the containing boundary of a body defines a three-dimensional region within itself, which is exactly the extension occupied by the body.

Aristotle had indeed defined the soul as the “form of the body,” or as the body’s “perfection (entelecheia).” He went on to present the soul as a set of faculties, most of which are exercised through the body. This makes a certain amount of sense, if you think of soul first and foremost as a principle of life. It meant that Aristotle could ascribe souls to plants and animals, as well as humans, plants leading a life restricted to the functions of nutrition and reproduction, while animals display further capacities for self-motion and sensation. If the soul is the body’s form, though, then how could it exist independently from body? If it cannot, then the prospects look dim for a key tenet of Christianity, the survival of soul following bodily death.

In late antiquity, Plotinus had criticized Aristotle’s definition of soul precisely on the grounds that it would make soul dependent on body.3 Following Plato, he saw the soul as a substance in its own right, which is immaterial and has only a temporary relationship to the body. Christians could find the same attitude in ancient religious authorities like Augustine. On the other hand, Christians had reasons not to go too far in a Platonizing direction. Their religion centered on the incarnation of God, and was committed to the eventual resurrection of the body in paradise. So it was awkward to admit that the body is nothing but an incidental and unwelcome accretion onto the soul. The upshot was that medieval authors had not only an exegetical problem about what to do with Aristotle’s definition of soul, but also a philosophical problem: how to preserve the human soul’s exalted status as an immaterial substance, while still saying that one human person is a union of soul and body? The problems did not end there. For Aristotle, the soul has a whole range of different powers, ranging from the lowly faculty of nutrition, which we share even with plants, to the distinctively human capacity for intellectual thought. How then to show that there is unity, this time not between soul and body, but within the soul itself? If your distinctively human part is your intellect, it might seem that your lower powers would be incidental to you, no part of who or what you really are. One migh...

Blund recognizes the challenge presented by Aristotle’s original definition of soul as the form of the body, and embraces Avicenna’s solution, namely that the soul does exercise its powers through the body, but its relation to body is merely accidental

Then comes a remark

that may overturn our expectations about medieval philosophy, though these expectations have been overturned so often by now that they are as dizzy as the stage manager at a Parliament-Funkadelic show. Blund asks whether the soul isn’t a subject studied in theology. Yes, he replies, but only as concerns the soul’s reward and punishment. The question of what soul actually is has nothing to do with theology

Like Plato, Blund argues that if soul is the principle of life, then being alive is intrinsic to soul. So it is no more susceptible to death than a triangle is susceptible to having angles that fail to add up to 180 degrees (§317; compare Phaedo 106b–d). As an immaterial thing, the soul is simple as well as immortal, notwithstanding its numerous faculties, which form a unity within it the way that species are unified within a single genus (§40). On the other hand, only the rational aspect of the soul survives after the body’s death, since it is the aspect whose power can be exercised without using the body at all. At this point, we might wonder when the theologians are going to burst through the door, insisting that they want to have a say after all. They may complain that Blund is making the soul sound very much like God: simple, immaterial, and eternal. How, then, is it that the rational soul falls short of divinity?

This idea, that even an immaterial substance like the soul may be constituted from more than one thing, is going to play a major role later medieval thought. For instance, some thinkers will say that it is thanks to some sort of composition that angels are distinct from God (see Chapter 70). Only God alone is perfectly simple. He is pure being, with no qualifications or specifications added. In this earlier period, the same basic idea is often expressed with the apparently rather paradoxical claim that incorporeal things are made of both form and matter. Obviously, the matter of something like a soul or an angel cannot be like the crude matter of bodies, but even an angel or soul does have matter. Here we can detect the influence of another thinker from the Islamic world, in this case a Jewish one, the eleventh-century philosopher Ibn Gabirol.6 He put forward a doctrine that attracted both admiration and condemnation from Latin medieval thinkers. We know his theory under

the name of “universal hylomorphism,” which sounds a bit like it could be a Parliament-Funkadelic song (who, I think it is not entirely inappropriate to observe, released a track called “Funkentelelechy,” which could in turn be the soul of a German radio operator). Ibn Gabirol’s idea was that everything, apart of course from God Himself, is composed from both matter and form. Among other advantages, this would ensure that only God is perfectly simple.

But William thinks soul is a special kind of individual, which is free from matter. To prove this he again makes use of Avicenna. He argues that if soul is capable of thinking about a simple and immaterial object of the understanding, then it must itself be simple and immaterial

Yet William does lay great emphasis on the soul’s guaranteed knowledge of itself. In a passage that evokes Augustine, while also prefiguring a famous passage of Descartes’ Meditations, William argues that the soul could never know

that it does not exist, because the soul’s knowing anything presupposes that it does exist (§1.4). Moreover, to deny the existence of soul in the impressively functional human body would be like seeing an expertly steered ship and denying that it has a helmsman (§1.7). To his credit, William anticipates the objection that may leap to mind for the modern reader: some machines are capable of very impressive functions despite being lifeless and without soul. William’s version of the objection considers a water clock. He says that this is no counterargument at all, because human intervention is needed to set up the water clock and keep it functioning properly (§1.7). He also singles out for criticism Alexander of Aphrodisias, the most important late antique commentator on Aristotle. William is appalled by Alexander’s suggestion that the soul could somehow emerge from, and hence depend on, the physical states of the body. This must be wrong, because the soul is superior to the body, and the better can never be generated by the worse. Besides, William adds, the soul is a substance, so it cannot just be an accidental side effect of bodily composition (§5.3–4).