Saturday, 23 July 2011

Question 53 - The Local Motion of Angels

Why this Question Matters.

In Ia.q52 Aquinas has argued that we can consider angels to be “in place” in a sense that is determined by the way that they exert their power in the world; they are where they act. Having dealt with the topic of statics, it would seem entirely reasonable to turn to the field of dynamics; in what way can we say that angels move? Local motion through space naturally involves time; indeed it is motion that, in the general sense of change, determines what we understand as time. Recall from the discussion in Ia.q10, that God is in eternity, angels are in aeviternity and matter-form composites are in time. If we ask the question of how angels can be considered to move in space and time, then we have to ask about what the interface between time and aeviternity might look like.

The Thread of the Argument

A1: The first question that Aquinas has to turn his attention to is whether it makes any sense to talk about an angel moving from place to place. In considering this question, he first of all thinks about what we mean by local motion in the case of ordinary material objects. When we think about objects moving we notice that their movement is continuous both in space and in time; things simply don’t jump from one place to another instantaneously. Indeed, it is this fact that leads us to model time and space as continua and to model motion by using considering location to be a continuous function of time. There is always a point in time between two different points in time; on any path between two places there is always an intervening point between any two different points.

When we turn to the angels we have to remember that they are said to be in place simply by the fact of their exercise of power in that place. If we are to say that they move, we are simply saying that the location of their exercise of power moves. As such, there is no reason whatsoever that impels us to think of that motion as being continuous. If they exercise their power, first in this place and then in that place, the change of place from one to another need not be continuous. Of course, it is perfectly possible that their motion may be continuous if it involves the continuous movement of the location of the application of their power. So Aquinas’s answer to this question is a guarded yes; we can consider angels to move locally, but we must be very careful not to confuse such motion with the local motion of material bodies.

A2: A corollary of the possible discontinuity of the local motion of an angel is that, unlike the local motion of a material body, he need not pass through intermediate points between here and there in his motion. To us, centuries after the invention of the calculus and more than a century after the careful analytical investigations by nineteenth century mathematicians into the nature of continuity, this is completely unsurprising and not at all difficult to prove. But Aquinas was writing before even the Oxford Calculators had started their seminal work; he spends a careful paragraph or two describing what it means for the motion of a material body to be continuous and he shows that if a motion is not continuous then the “intermediate” property of continuous motion fails. His analysis may not possess modern rigour, but what he could do is rather humbling.

A3: The other part of the equation when considering the possibility of discontinuous motion is that it must surely involve an instantaneous “jump” from one place to another. However, there is a problem with this.

Suppose we are timing material motion with a stopwatch. If we time a runner running the hundred metres race, we start the stopwatch at t = 0 when the gun fires and the runner starts running. The runner runs (continuously) from the start line to the finish line and arrives at the finish line at (say) time t = 10. Because the motion is continuous, the runner is at a particular place at every time between zero and ten seconds. Now let us try to do the same thing with an angel who moves discontinuously from the start line to the finish line. Let us suppose the angel arrives instantaneously at the finish line at time t = 10. Where is he at t = 9.9? He is at the start line. What about 9.99 seconds? Similarly he is at the start line. What about 9.999 seconds? There’s a pattern emerging here! There is no last time at which the angel is at the start line before he transitions to the finish line. The problem is that our very notion of modelling the motion of material objects using spatial and temporal continua is predicated upon the continuity of that motion. When we run into an example like angelic motion that is discontinuous, we must realize that this fails.

Aquinas draws the obvious conclusion: we cannot model discontinuous angelic motion using continua (there no problem with continuous angelic motion). The discontinuous motion of angels takes place in a discontinuous or discrete time. At one discrete time point an angel is here and at the next discrete time point the angel is there; we cannot say that this motion is instantaneous because there are no time points (for the angel) between the start and finish times.

Handy Concepts

  • Angels can be said to move in space insofar as their power is exercised first in one place and then in another. This movement can be continuous or it can be discontinuous.
  • In discontinuous motion an angel need not pass through intermediate places between his start and his destination.
  • An angel’s discontinuous motion cannot be measured by continuous time; rather it is measured by a discrete time. Hence we cannot say that discontinuous motion occurs instantaneously.


  • Aquinas’s solution in the third article is a fascinating anticipation of some the problems of time that arise in quantum mechanics. In some quantum mechanical systems, it does seem to make sense to model time and space as discrete variables.
  • Perhaps Aquinas’s solutions to the problems raised by angelic motion are a little more restrictive than they need be. The fundamental insight that an angel may be considered in place by the exercise of his power there, or by his potential to exercise power there, remains of fundamental importance. But Aquinas doesn’t seem to push some of his ideas far enough. For example, he asserts that an angel cannot be in more than one place at a time, but allows that that place may be spatially quite complex (the fundamental issue being that the place is determined by the needs of the determined exercise of power rather than anything to do with how the actors in that exercise of power are arranged). This being so, the movement of an angel from place to place corresponds to the shift of focus from one act of determined power to another. The act of determination of the angel to its act of power may be instantaneous, but does this force the application of that act of power in the material world to be instantaneous? Might we not consider such acts of power as coming-to-be in time in the material world? Pictures such as a spherical surface descending to intersect a plane surface may then be helpful. Elaborations of this picture are then helpful in eliminating the implication that angels’ discontinuous acts need to occur in discrete time.
  • Aquinas never really ties up the connection between time and aeviternity in this article, which is a bit of a disappointment!

Question 52 - Angels and Space

Why this Question Matters.

In the material created world that we see around us, we’re quite comfortable with the idea that things occupy a certain delimited portion of space; in the jargon of medieval philosophy, we say that they are in place. For the more reflective, the only difficulty with this picture might be the question where am I? When we think about ourselves, we might ask about where our souls are, about where the seat of our being is. Despite the rare reports of “out of body” experiences, we are probably most comfortable with the thought that our souls are intimately connected with our bodies (even if we demur from being more specific than that). We are in place, because our material components, our bodies, are in place. What about a purely spiritual being like an angel? We’ve seen above that Aquinas considers that, although angels may make use of a body for certain functions, they are incorporeal and not composites of matter and form. How does such a pure form interact with the material world? Can we say that an angel is located in space and in time? Is an angel in place?

The Thread of the Argument

A1: Aquinas doesn’t have a lot of material upon which to found an answer to the question of whether we can say that angels are located in space and time. Indeed, this is one of those occasions where he attempts to take the scanty data provided by revelation and to build a coherent answer to a question not directly addressed by that scripture. Here we have the information that angels are present in some way to the people that they appear to and that they exercise some sort of “power” in space and time; we also know that they are not matter-form composites and therefore the category of “quantity” does not directly apply to them. When we think about how material objects are in place in space and time, we think in terms of their quantity; for example, this much being in this place gives us concepts such as volume and density. Aquinas claims that we should think of the presence of angels in space and time in terms of what he calls their power quantity. What he means by this is that it is only by the exercise of their power at a particular place that we recognize that they are present in that place; therefore the exercise of such power (or the potential to exercise such power) in a place provides an analogue to quantity that allows us to say that angels are in place.

Aquinas is very careful to warn about how the parallels between how an angel is in place and how a material body is in place have to be understood. For example, we can’t say that an angel is currently two metres wide or that he is at particular coordinates in the space time continuum or that he is contained in this room. Rather we have to understand the angel as acting upon this region of space and time, from outside of space and time as it were. It is by this acting (or power to act) that the angel is present in place, not by his being in that space and time in the way material objects are in space and time.

A2: God is omnipotent and omnipresent in that omnipotence. Seeing that pure spirits like angels seem to be more like God than we are, and are localized in a place by the act of power, we might ask whether angels can exercise that power in more than one place at a time. In other words, can they be in several places at once?

Aquinas is careful to point out that it is easy to be misled by thinking of the being-in-place of angel in the same way that we think of the being-in-place of a material object. We mustn’t think of an angel “being here” and “being over there”, rather we must think of an angel being where he is by where his power is directed. As such, we must think of his act of power as being determinate to a particular task; God’s power acts everywhere in everything, but an angel’s power acts on a particular determinate task. As an example, our Guardian Angels are present to us at all time; they don’t moonlight on some other task at the same time. Therefore, in the sense that an angel is in place, he is in only one place. However, the exercise of an angel’s power cannot be localized in a material sense to a particular point in space and time but rather is associated with wherever the exercise of power is occurring. Therefore an angel may be exercising his one determinate act in a region of space that may be extended (and which may even be disconnected).

A3: Dual to the question of whether an angel can be in more than one place at one time is the question of whether more than one angel can be in one place at one time. Because Aquinas has defined the notion of place for an angel in terms of the power that the angel exerts in a place, his answer to this latter question is immediate. One and the same thing cannot depend entirely and immediately on more than one cause, therefore two angels cannot exercise their power in the same place at the same time and therefore there cannot be more than one angel in a place at one time. We must be careful to understand that this does not preclude, for example, two angels being present in the same room. What it bars is the two angels “overlapping”; they cannot both carry out the one determinate action.

Aspects of this answer may seem puzzling. In the material world, we are quite used to the idea of causes collaborating or coming together in some other way in some action; can’t this be true of angels as well? Aquinas appears to be arguing a very subtle point here. If we think about two people pulling on a rope attached to a boat in a canal then in one sense we are quite justified in thinking of their causality acting together in some way to pull the boat along. But in another sense we might think of the power of one person acting on one segment of the rope and the power of the other acting on another segment. The power of these two pullers may be considered to act through the rope to form one power acting on the connection between rope and heavy object. Aquinas seems to divide any possible collaborative activity this way when it comes to angels. The power of acting of an angel is a determinate power of acting and at such a level of determination it is not shareable.

So if we think of examples such as the possession of someone by many evil spirits (e.g. Mark 5:9, where the spirit is spoken of in singular and plural terms) we might wish to consider the possession as a singular thing, but we should more rightly consider it the action of a multitude of spirits each acting in its determinate way, each different within the subject of the possession.

Handy Concepts

  • Angels are “in place” only in the sense that their power acts in a determinate fashion in a particular place in space and time. We must not think of their being in a place as suggesting that the place circumscribes or contains them.
  • Consequently, angels are localized to being in one place at one time in the sense that they carry out determinate acts of power at particular places.
  • Angels cannot “overlap”; the power of each angel acts to a determinate end that precludes more than one angel being in the same place at the same time.


  • In the summa, Aquinas appears to associate the notion of “being in a place” for an angel with the actual application of an act of power in that place. This would seem to limit an angel to being present in a place only when it is acting on that place; would this be true, for example, for our Guardian Angels that are always present to us? In what way are they always actually acting? In the later Quodlibetal Questions Aquinas appears to loosen his definition to allow that it is the power to act in a place rather than the actual exercise of that power that defines the notion of “in place” for angels.
  • In article 3, Aquinas’s reasoning that two angels cannot be in the same place at the same time is crying out for a more extended treatment of causation in general.
  • The post-medieval mocking of the scholastic age for allegedly debating the question of how many angels can dance on the head of a pin simply demonstrates the degeneracy of post-medieval thinking.

Friday, 22 July 2011

Question 51 - Angels and Bodies

Why this Question Matters.

We have seen in Ia.q50 that angels are incorporeal and that they are not compositions of matter and form. However, the testimony of revelation relates the appearance of angels as messengers of God to men; this would seem to imply that angels are using bodies in some way or are related to bodies even if they are not bodily themselves. Perhaps we should think of these appearances of angels purely in visionary terms; their being is directly placed in the mind of the seer. In this question Aquinas seeks to sort out the questions that such appearances raise with the metaphysical treatment that he has developed so far.

The Thread of the Argument

A1: Aquinas asks first whether bodies form part of the nature of angels. This is a question distinct from that answered in Ia.q50; here we are concerned with a relationship to bodies looser than that implied by the claim that angels are corporeal or that they are composed of matter and form. Even in this looser form, Aquinas answers in the negative: the possible use of a body by an angel for a particular task need not imply that the presence of a body is natural to an angel but rather it should simply be considered incidental.

Later in the summa, in Ia.q75.a2, Aquinas will argue that the act of understanding is not an action of a body or of a bodily power and that therefore the possession of a body is not in the nature of a purely intellectual being. Now Ia.q75 is in the section of the summa dealing with human nature and we immediately notice that humans are intellectual creatures that are united with bodies! Here Aquinas anticipates the later argument by pointing out that the union of soul with body in the intellectual creature man is due to the weakness of human intellect; we need our bodies in order to inform our intellects. In the case of angels, this is not so: the angel intellect is so powerful that is has no need of a body.

A2: Having argued that angels have no need of bodies as regards their natures, Aquinas now turns to the question of whether they might “assume” bodies for some particular purposes such as to appear in bodily form to humans. This is precisely the position that Aquinas takes with respect to the scriptural accounts of such appearances. He dismisses the suggestion that they might simply be “visions” occurring within the imagination of the recipient, as the appearances are not restricted to the intended recipient. Angels do not assume bodies for their own purposes but for our benefit; moreover this assumption, as it is recorded in the Old Testament, is a symbol of the future assumption by the Word of God of a human body. This “assumption” is not as a union of form and matter nor yet is it simply like a puppet master pulling the strings of a puppet. Rather it is a representation of them that represents what is intelligible in them.

A3: Angels assume bodies for some particular purposes, but what is the nature of these bodies? We’ve seen that Aquinas argues that at one extreme they are not simply lumps of matter that are manipulated by the angel nor, at the other extreme, are they a union of the form of the angel with the matter of the assumed body. Still, can we go so far as to attribute life to these bodies? Aquinas argues against a wooden literalism in the interpretation of the scriptural texts. Although the latter are phrased as though angels perform many bodily tasks, their function is figurative. As the reply to the first objection puts it: “these bodies are assumed only in order that the angels’ spiritual properties and their spiritual operations might be depicted by means of human properties and human operations.”

Handy Concepts

  • It is not of the nature of angels to have a necessary relationship to bodies.
  • Angels may assume bodies for particular purposes such as the communication of God’s will to men.
  • The bodies that angels assume provide representations of the angles spiritual natures in corporeal form.

Question 50 - The Angelic Nature


Aquinas introduces this question with a brief road-map that covers much of the rest of the first part of the summa. Questions 50-64 are to be devoted to purely spiritual creatures (the so-called “Treatise on the Angels”), Questions 65-74 to the purely corporeal elements of creation (the so-called “Treatise on the Six Days”), and Questions 75-102 are devoted to those creatures that include both spiritual and corporeal elements in their being (the so-called “Treatise on Man”). If we refer back to the introduction to Ia.q44 (at the start of the Treatise on Creation), we see that Aquinas is leading us through the different types of being created by God. The very final part of the first part of the summa, from Ia.q103 onwards, will be devoted to the governance of creation; that is, the relationship between God and the created order.

In this, the “Treatise on the Angels”, Aquinas will consider created beings that are purely spiritual. He will describe their substance (in Questions 50-53), their intellect (Questions 54-58), their will (Questions 59-60), and their creation (Questions 61-64).

Why this Question Matters.

It is a doctrine of the Christian faith that the beings called “angels” exist. But the sources of revelation about the nature of these angels is quite scanty: we know quite a lot about their function (the word “angel” derives from the word in Greek meaning “messenger”), but very little about what they are. Aquinas has built up a coherent metaphysical framework of being that allows us to talk about God and about material things; it is now time for him to describe how non-material but created things might fit into this framework.

The Thread of the Argument

A1: From a modern point of view, the idea of the existence of Angels seems a very strange thing. Their existence is attested to in the sources of Christian revelation and is therefore a truth of the faith in the Christian religion. However, one might ask whether the existence of the Angels is purely a truth of faith or whether there are any other grounds that might justify belief in their existence; for example a demonstration based in natural theology. Of course, we must also ask what these angels are supposed to be: what is their quiddity? Aquinas starts the “Treatise on the Angels” from the point of view of the necessity of the existence of incorporeal creatures; as such this section of the summa fits into a wider inquiry into what is included in the whole of creation. Aquinas argues that the existence of incorporeal creatures is necessary because God has created creatures principally for their assimilation to God; they come out from God and return to God. Perfect assimilation of an effect (a creature) to its cause (God) occurs when the effect imitates the cause with respect to the way that the cause creates the effect. As God creates the universe through his intellect and will (Ia.q14.a8 and Ia.q19.a4), the perfection of the universe requires there to be purely intellectual creatures. As an act of the intellect is not the act of a body or of a corporeal power, there must be purely incorporeal beings.

A2: Having disposed of the question of whether angels could be corporeal, it might seem odd that Aquinas now asks whether angels are composed of matter and form, for this latter would seem to imply that they are corporeal. The point is that Aquinas is addressing theories current in his time (especially among Franciscan theologians) that there might be some sort of matter-form composition in angels even if it isn’t the same sort of matter-form composition that exists in everyday objects. Aquinas traces the roots of some of this current thinking back to the Jewish philosopher Avicebron, who flourished in the eleventh century. According to this theory, a sort of “cosmic matter” becomes specialized to “corporeal matter” in bodies and “spiritual matter” in spiritual beings in composition with their respective forms. Aquinas rejects this idea, pointing out that it stretches credibility to try to make this consistent with intimate connection between matter and the notion of quantity. Moreover, Aquinas insists that the very nature of spiritual beings is that they are purely intellectual and that therefore, because of the nature of the intellect, they cannot admit of any composition with matter. Aquinas will return to the theme of the essential non-materiality of the intellect in Ia.q75.a5, but the argument boils down to the fact that if matter was essentially involved in the operation of the intellect then the reception of forms in the intellect would involve the composition of that form with matter, created a new individualized version of what is comprehended.

There are still some troublesome objections to be met. The matter-form composition gives us the genus and difference that allow us to distinguish things within a genus; without the matter-form composition we seem unable to make such distinctions. Aquinas argues that we cannot carry over so easily what we know about material objects to the spiritual world. In the spiritual world there is no correspondence to the material distinction between the determined and the determining; rather, each being of itself occupies a distinct degree in the scale of being. This will lead Aquinas to argue in article 4 that each individual angel occupies its own species within the genus “angel”.

Perhaps more troubling is that in material things the composition of matter and form corresponds to the actualizing of potentiality of matter by form. It would seem that without this composition a spiritual being must be considered pure act and not limited by matter and therefore infinite. Spiritual beings are beginning to sound a bit too much like God Himself for comfort! Aquinas points out that the composition of matter and form is not the only composition that must be considered when we think about actuality and potentiality: there is also the composition of essence and existence. It is this composition of “that which” and “that by which”, held in being by God, that distinguishes the pure actuality of God from the high-but-not-pure actuality of the angels.

Similarly this composition of essence and existence limits the spiritual creature to be a particular being and thus, absolutely speaking, limits it to be finite. But, as Aquinas points out in the spirit of the neo-Platonic liber de causis, we might consider such spiritual beings to be “quasi-infinite”. To illustrate what this means, he considers the example of “whiteness”; if whiteness could subsist on its own it would be non-finite inasmuch as it would not be limited to being this-particular-whiteness in this particular object. However, it would still be finite, absolutely speaking, as its being is that of a particular determinate type of thing. So, if we looked “from above”, from God’s point of view, purely spiritual beings would be determinate finite beings. If we look “from below”, such pure forms have a certain sort of infinitude.

A3: How many angels are there; only a few or many? After reviewing the approaches of Plato, Aristotle and Maimonides to this question, Aquinas comes down on the side of “many”. Not only does scripture appear to support this position, but one might argue that God would produce more things of a more perfect nature in creation. In the spiritual world such plenitude is represented by number rather than extent, so we may infer that the number of the angels far exceeds the number of material things.

A4: If we think about how angels might differ one from another, we might consider that any differences that they do have are differences of degree rather than of kind. Aquinas, however, disagrees: each angel occupies its own species in the genus of “angel”. This follows from the argument of article 2 that there is no composition of matter and form in angels. Because matter is the principle of individuation of things there can be no individuation of angels within a species. Each angel fully realizes the actuality of what its essence can be; that is, the composition of essence with existence fully determines what the angel is, there is no alternative determination of the angel.

Aquinas gives a helpful analogy carried over from article 2: if we consider “whiteness” purely as a form, it makes little sense to talk about different “whitenesses” as forms as opposed to different realizations of whiteness in things. When we say that the whiteness of this object differs from the whiteness of that object, we are simply saying that the form “whiteness” is realized differently in the two objects, not that there are two different “whitenesses”. “Whiteness” is multiplied by being instantiated in different matter; this is not something open to the essence of an angel.

A5: Aquinas has argued that angels are not a composition of form and matter but are a composition of essence and existence. It follows from this that angels are naturally immortal. What this means is that once an angel has been brought into existence its nature is such that it will not, by the course of nature, perish. This does not mean that an angel is a necessary being in the way that God is a necessary being; an angel’s continued existence depends on the First cause maintaining the composition of essence and existence in it.

Aquinas argues for this position by observing that things perish by the separation of their form from their matter. If we think about non-human material objects, we observe that a matter-form composite not only has potentialities to lose and gain accidental forms but it also retains the potentiality to lose its current substantial form and gain a new substantial form. So, a duck can not only lose its current plumage and gain a new one (whilst still remaining a duck) but it can cease to be a duck and become a duck-corpse. (More strictly, the matter of the duck is at first informed by the form of a duck and is then informed by the form a duck-corpse). It appears to be an inherent feature of matter-form composites that they have a potentiality for the eduction of a new substantial form: within them lie the seeds of their own destruction. When we turn to the consideration of angels, we observe that they have no matter, therefore they cannot perish in this way: they can only cease to be by God ceasing to cause their essence-existence composition. We might even say that they are naturally immortal and supernaturally mortal!

Handy Concepts

  • As God creates the universe by means of his intellect and will, it is fitting to the perfection of that universe that there be purely incorporeal spiritual creatures as part of that creation.
  • As angels are purely intellectual creatures, there is no composition of matter and form in then, rather only a composition of essence and existence.
  • There are many more angels than there are material objects.
  • Each angel is unique to a species.
  • Angels are not a composition of matter and form and therefore they are naturally immortal. The only way that an angel can cease to exist is by God withdrawing the cause that maintains their composition of essence and existence.


  • Although it may seem at times that Aquinas’s treatment of the angels is ad hoc, simply trying to fit the data of revelation, it might better be seen in more principled terms than that. Aquinas has identified various compositions that underlie the being of things: matter-form, essence-existence, and actuality-potentiality. Having identified that it makes good metaphysical sense to talk about a being (God) that is pure actuality and in which there is no composition of essence and existence or of matter and form, it would seem perfectly reasonable to investigate whether there can be beings that are compositions of essence and existence but not of matter and form.
  • Having talked about the natural immortality of the angels, one is immediately drawn to the question of the immortality of the human soul. We have already observed that for non-human material objects, the composition of matter and form can go out of existence and that the forms of such things go out of existence with the material object. Yet for the angels, there is a natural immortality because there is no such matter-form composition. The intellectuality of the form of an angel demands its non-materiality and it is in this intellectuality that its subsistence, the seed of its natural immortality, lies. When we turn to human beings we are met with a mixture: we are composites of matter and form and yet we also possess an intellect. As such we perish but our form, being an intellectual form, must continue in being. Aquinas will return to this issue in Ia.q75.

Sunday, 3 July 2011

Question 49 - The Cause of Evil

Why this Question Matters.

We’ve seen in Ia.q48 that evil is not an entity that has its own being, but rather is a privation in a good. It still remains to be seen, however, how evil comes about. Following his general metaphysical drift, Aquinas must ask about the cause of evil; after all, if it can be said to be present in a subject in some sense (Ia.q48.a3) then it must have been caused to be present in that subject. So then, what does it mean for evil to be caused? Again, as in Ia.q48, there’s a lot at stake behind this seemingly innocent metaphysical question. God is the first cause of all that is in creation so it would seem that we must attribute evil, even if only at the end of a long chain of causality, to God’s causality. The alternative would seem to be some dual principle in the universe, some most evil source of all evil. Is Aquinas finally caught between Scylla and Charybdis? Read on!

The Thread of the Argument

A1: We saw in Ia.q48.a3 that a good can be the subject of an evil, in the sense that for an evil to exist there must be a good that is suffering the privation that corresponds to the evil. But if this is so, can we go even further and say that any evil must be caused by a good? It’s clear that any given evil must be caused in some way. Evil is the privation of the good, so there must be some cause of that privation; something that prevents the subject of the evil from achieving the actuality it should achieve. Of course, the only things that can cause are those things that are actual, and things that are actual are good insofar as they are actual. Therefore every evil must be caused by some good.

However, Aquinas is not willing to let the question rest there; he wants to enquire into how evil is caused. He points out that the enquiry of Ia.q48.a3 implies that the subject of an evil is a cause of that evil in the sense of being a material cause. However, since the existence of evil consists in a privation of a form rather than the existence of a form, it cannot have a formal cause. Similarly, it does not have a final cause as it corresponds to a lack of a fitting end.

Even more than this, Aquinas argues that when we consider efficient causes, we will see that evil comes about per accidens rather than per se. To see this, consider an agent bringing about an action. If the agent is doing what it is meant to be doing, bringing about its proper effect it may still happen that some patients become collateral damage to the agent’s proper effect. There is no necessity for the boulder rolling down the hill to crush the tree that lies in its path; the evil caused to the tree is per accidens. On the other hand, if the agent is failing in its proper effect, this can happen because of a defect in the agent (for example, a young animal may not have learned how to run well) or in an instrument used by the agent (a broken leg tends to inhibit running, for example). Again, both of these cases are per accidens rather than per se to the cause. Finally a properly acting agent may cause evil in a defective patient: a piece of machinery may break because one correctly functioning part may mesh too hard with a defective part; as before, this is per accidens to the proper action of the agent.

So, although we must say that evil is caused by a good, it is caused in a somewhat peculiar and negative manner. It has a material cause in the good that is the subject of the evil; it has not final or formal cause because it corresponds to a privation of these in some good; and although it has an efficient cause, it comes about per accidens from its efficient cause. All this reinforces the idea that evil is not an entity in itself, but rather a privation in a good that results from a falling short in some way of the actualization of that good.

A2: Behind every secondary cause acting in creation is the first cause, God. Therefore God must be the cause of every evil. When it comes to the malum poenae, Aquinas is willing to concede this. The form that God intends in created things is ordered to the good of the whole universe. In Ia.q48.a2 we saw that part of the goodness of the universe inevitably requires the failure of some created things; but the important point that Aquinas wishes to make is that this failure is a per accidens feature of God’s causality, following the reasoning of article 1 of this question. The scriptural passages (such as 1 Kings 2:6) where death as well as life are attributed to God should be interpreted in the light of the per accidens nature of such causality (along the lines hinted at in Wisdom 1:12-15).

When we consider the malum culpae attributed to rational creatures, however, things are different. The defect in their action is caused by the defect in the agent causing the action, in line with part of the analysis presented in article 1. Therefore such defective action is not to be traced back to God.

A3: If there are evils that cannot be attributed to God, then perhaps there is some greatest evil to which they can be attributed as first cause. Given the machinery that Aquinas has already set up, it comes as no surprise that he can rapidly dismiss this idea, giving three reasons. In the first place, although the first principle of good things is good through His essence, this cannot be the case with any putative first principle of evil; any thing which exists is good insofar as it exists, and also evil does not exist except in a subject which is good. Secondly, although evil can diminish a good it cannot destroy if (Ia.q49.a4), so some good must always remain. If not, evil would reduce itself to sheer nothingness. In the third place, we have seen in article 1 that every evil is caused by some good and evil cannot itself be a cause except per accidens. As such, it cannot be a first cause as some per se cause would have to underlie it.

In the reply to the fifth objection, Aquinas makes an interesting observation. He denies that in creation evil is present in most things; much of the created universe is incorruptible and not subject to an admixture of evil. However, when we consider humans, the situation is different: evil appears to occur in most cases! Most humans follow the apparent goods offered to them by the senses whereas the true good for man lies in following the correctly ordered reason.

Handy Concepts

  • There is a sense in which what is evil is caused by what is good. However, evil has no final or formal cause. The material cause is the subject that suffers the privation corresponding to the evil. Efficient causes of evil act per accidens rather than per se.
  • God can be considered the first cause of malum poenae but not of malum culpae; the cause of the latter is attributed to defects within the agent.
  • One cannot trace back the cause of evil to some maximally evil first cause of evil in the way that one can trace back the causes of being to the first cause of being.


  • In article 2 Aquinas skates very quickly over the possibility of God’s causing sin. The answer given, that the defect arises from a defect in the agent, does not even begin to address how God’s providence could have allowed that defect to come to be nor does it address the question of how a defective agent is moved to its defective act. For example, someone with a malformed conscience may place an act that is objectively disordered. How, then did their conscience come to be in the state that it is in? Moreover, when we consider the actual act itself, how could it come to be without God acting as first cause behind any secondary causality that may act? Aquinas’s speedy dispatch of this issue at this point in the summa may be attributed to the fact that he hasn’t yet developed enough metaphysical theory to cover it adequately. After all, if we are to consider the sin, we need to have discussed the sinner; this Aquinas does later in the first part of the summa in questions 75-102. Also, we need to consider how God acts in creation; what can we say about how the first cause moves secondary causes to act. Again this is covered towards the end of the first part. For the moment, Aquinas is satisfied in stating that it is so, without really explaining how it is so.

Saturday, 2 July 2011

Question 48 - The Distinction Between Good and Evil

Why this Question Matters.

At first sight, this question and the next may seem oddly placed in the account of creation. Aquinas, however, has been concerned to explain the diversity amongst created things and he considers that the distinction between good and evil is of fundamental importance in this account. Lurking in the background to this question is the spectre of dualism; the idea that in the world (both created and uncreated) there are two principles: one good, the other evil and that they are constantly in battle with one another. It is a matter of great urgency within Christian belief to affirm that all that the creator God creates is good insofar as it has being. In this question and the next, Aquinas enquires into the nature of evil and into its origin in the world, affirming the traditional teaching that evil is privation of the good rather than a being with its own existence.

The Thread of the Argument

A1: One of the most fundamental questions about evil is “what is it?” In this question, Aquinas asks whether evil is something real; a reality opposed to the good. It’s important to remember that when we read about Aquinas talking about “evil” he is actually using the Latin word malus, which has a much broader meaning than the modern English use of the word “evil”. These days, we tend to restrict the use of the word “evil” to moral monstrosities; for Aquinas a broken chair leg is an “evil”. For Aquinas, malus is the absence of a good in something that should have that good by its very nature; so a broken chair leg is malus because it can’t be a particularly good chair leg if it is broken!

The position that Aquinas is going to argue against is that evil has its own reality. The main thrust of the objections to Aquinas’s position is that when we look at evil acting in the world it does appear to do precisely that: to act. It appears to be some sort of contrary to the good and to have the ability to act against the good. Anything that has the ability to act in this way, and to be a contrary to something that is real, must itself be a real thing.

Aquinas answers that to understand the opposition between good and evil we must look to analogies such as the opposition between light and dark rather than to that between two opposed agents. We realize that our notion of darkness arises from an understanding of light and corresponds to an absence, a privation, of light. Now, everything is good insofar as it has being and every reality tends towards its own being and perfection. Therefore we should understand evil as a failure to move towards that being and perfection; evil is a lack, a privation, in what it is for real things to be what they are ordered to be.

The second objection points out that, in the field of morality, a good habit differs in species from a bad habit. This would seem to indicate that bad habits are a different species of reality from good habits. In his answer to this objection, Aquinas develops his main answer to the question by arguing that when there is a privation in something, there is not a privation down to complete nothingness. Rather, there is some being that remains short of the being that should be. So, for example, when somebody chooses to do something completely stupid, it is not that they are entirely lacking reason, but that they are choosing some apparent good (that should be considered good in reality insofar as it has being). Aquinas takes this line of thought further in his answer to the fourth objection, which claims that evil appears to act in the world and therefore must be a reality. Against this, a distinction has to be made in what it means to act. In the first place, something can act as a formal cause, as when the form of whiteness makes something white. In this case we can say that evil “acts” as a privation, in being a lack of a particular form in something. We can also consider acting as efficient cause (the painter makes the wall white) or as final cause (the end is chosen for the wall to be white). Again, in these two cases, evil isn’t doing anything per se, as a reality in itself. Rather, evil “acts” insofar as some other reality (what is actually done or what is actually chosen), that falls short of the perfection of the entity, comes to be. In this sense we can say that evil is always conjoined to some good.

A2: Having determined that evil is not a thing, not a reality in itself, we would be inclined to think that we cannot say that there could be evil in things. Aquinas resists this, however. He has already explained (in Ia.q.47.a2) that the perfection of the universe requires there to be an inequality amongst things. Now, one type of this inequality can be seen in the difference between mortal corporeal things that can lose their being and immortal incorporeal things that cannot. So it would appear that the perfection of the universe requires there to be some things that can fail with respect to their goodness (and others that do not). To this extent we are justified in saying that there can be evil in things.

In reply to the second objection, Aquinas makes the important point that we can be misled by the language of being. There is a difference between being as considered the being of a thing (this is the sense in which the transcendentals “being” and “thing” are convertible) and the being expressed in the truth of propositions as when we say that there is blindness in the eye. In the former case we are making a positive expression of the being of something, in the latter we’re actually expressing a lack of being.

The third objection touches on the general “problem of evil”: it would appear that what is better is that which has less evil mixed with it; God always makes what is better, therefore there cannot be any evil in the things made by God. Aquinas answers that we should consider the totality of what is made by God; this is better if it contains things able to lose their good. Underlying this position is the belief, handed down from St. Augustine, that God can do good even with evil, so that many goods (such as a lion) would not exist if some evils (such as the ass being eaten by the lion) did not exist.

A3: We’ve seen that evil is not a thing (article 1) but that we can say that evil is in things (article 2). Can we be more precise about how evil is in things, if it not a thing itself? In this article, Aquinas asks if evil can have good as its subject. What this means may sound a little obscure, but Aquinas’s meaning becomes clearer when we inspect his reply.

There are two ways we can look at the absence of good. In the first case (where this absence is a negative) a particular good may not be present in a situation where it would not be expected to be present. So, we would not expect a man to be able to run as fast as a deer or to have the strength of a lion. This sort of absence is a simple absence and cannot be considered an evil in any way. By contrast, where a good is not present where it should be present, then this is a privation and represents a true evil. An eye should provide the function of sight; if it doesn’t, it is suffering a privation; blindness is an evil in this sense. The fundamental difference between these two situations is that in only one of the cases do we have a being that is in potentiality to something; the eye is in potentiality to having its sight, even though it doesn’t actually have it. Moreover, the subject of the privation of sight (the potentiality) is the same as the subject that is in actuality (the eye without sight). In this way, we can always consider evil as having some good as its subject, because it is always associated with the subject suffering the privation; privation is a negation-in-a-subject rather than a straight non-existence. As Aquinas notes in the reply to objection 3, the subject of the evil is not the good that opposes it but the actuality in potentiality to the good. So “sight” is not the subject of “blindness” but rather the blind eye is the subject of blindness.

A4: Can evil totally destroy the good? If one though of evil as an entity, then the idea of evil destroying good would seem quite reasonable. But if evil is a privation, then a total lack of good would seem to be non-being rather than any sort of depraved being. Aquinas answers this question by making distinction between what we understand by “good”. He is quite willing to affirm that the good of sight is completely destroyed by the evil of blindness. On the other hand, that good which is the subject of evil (see article 3) is not diminished at all by evil, as a good in itself. This latter may seem puzzling, but what Aquinas means is explained as he continues his answer. If we consider the unseeing eye not simply in its actuality as an unseeing eye (which is a good in itself) but in its potentiality to be a seeing eye, then we can say that evil diminishes the good. So it is as a potentiality that evil diminishes the good but not as an actuality.

The question then remains as to whether evil can diminish the good in this sense to zero. Aquinas argues that this cannot be so because, even if evil acted without limit, there would still be a subject with some actuality (and therefore a good) in potentiality to reversion to the good.

A5: One of the fundamental divisions in the understanding of evil is the division between the malum culpae (the “evil of fault”) and the malum poenae (the “evil of punishment or of pain”). Informally, one might think of the difference between these two as being the difference between bad things chosen by the will of a rational being and bad things that happen to an individual. The question asked here is whether this division is an adequate division for all types of evil.

Aquinas answers that evil is a privation of the good and that the good consists in a certain actuality in a being. Now we can divide actuality into first actuality and second actuality: first actuality is something that exists in a thing and second actuality is the operation of that thing. So, for example, I have learned how to speak French but I am not currently actually speaking it (first actuality) versus I am currently speaking in French (second actuality). Likewise, we can divide evil into that which corresponds to the privation of a first actuality (I am missing both legs) versus the privation of a second actuality (I have good legs but I am too lazy to use them to walk to the shops). In the first case, I can’t do something; in the second case I choose not to do what I can (and should) do.

So, if we restrict attention to those beings that have a rational will, the good is the proper object of the will. An evil in the first sense prevents me from doing something and has the character of an affliction or a pain or a punishment. An evil in the second sense is my choice not to choose a true good in favour of an apparent good and has the character of a sin or of a fault. So in rational creatures, at least, the division of evil between either malum culpae or malum poenae is appropriate.

If we think about non-rational creatures, however, this division is not appropriate. Bad things can happen to a stone (being crushed to dust, for example) but one can hardly say that they are a matter of fault or of punishment.

A6: Having discussed the division of evil into the malum poenae and the malum culpae in article 5, it might seem natural to ask whether punishment (or penalty) itself has more of the character of evil that sin does. Aquinas’s position is that sin has more of the character of evil than does punishment, even when punishment is taken in the most general sense, for example when the withholding of such things as grace or glory, things not strictly due to the rational creature, are considered as punishments. He gives two arguments in support of his position.

First, someone becomes evil because of the evil of sin, which consists in the disordered use of the goods that a person has by his will; whereas punishment deprives that person of an actuality and therefore the ability to act towards some particular good, but does not inhibit the good use of what the person does possess. Second, God is the author of punishment (depriving the creature of some good) but not of sin; the evil of sin is properly attributed to the misused free will of the creature.

Handy Concepts

  • The diversity amongst created things includes the distinction between good and evil; this distinction is that evil is a privation, or lack, of the good. Evil is not a being or entity in its own right.
  • In this question, Aquinas is talking about “evil” in the most general sense implied by the Latin word malus; this sense is much wider than is implied by modern use of the word “evil”.
  • Even though evil is not itself an entity, we are justified in saying that evil can be “in” things. Furthermore, the good can be the subject of evil in the sense that it is a “privation-in-a-subject”. The subject of evil is not the opposing good; rather it is thing suffering the privation.
  • Evil can diminish the good, but it cannot totally destroy it; there is always some being left that is the subject of the privation.
  • The division of evil into the malum poenae and the malum culpae for rational creatures follows the distinction between first and second actuality. The first corresponds to a lack in the creature that prevents full being or actuality; the second corresponds to the misuse of a first actuality in the creature.
  • The misuse of what we have has more of the character of evil that the absence of what we don’t have.


  • The division of evil, at least for rational creatures, into the malum culpae and the malum poenae may seem quite reasonable. That malum culpae be translated as the “evil of sin” or the “evil of fault” likewise seems quite reasonable. But understanding what the malum poenae really is and translating the phrase into English seems more challenging. The Latin word poena translates as “punishment” or “penalty”, but does this mean that Aquinas considers any form of evil that befalls an individual as a punishment from God? The key is in the body of his answer in the fifth article: “Therefore the evil which comes from the withdrawal of the form and integrity of a thing, has the character of a penalty; and especially so on the supposition that all things are subject to divine providence and justice, as was shown above (Ia.q22.a2)”. Aquinas holds short of claiming that every such occurrence of evil is a punishment; rather, in the light of the action of divine providence, he claims it has the character of the punishment. When we might say that we are suffering from the afflictions of life, we are reflecting a similar position to Aquinas; it is as if we are being punished. On this line of thought, Herbert McCabe suggest a more fitting translation of malum poenae to be “evil suffered”.
  • Aquinas’s treatment of evil in this part of the summa is very condensed. For a much more extensive analysis of evil, his “Disputed Questions de malo” is a must. For a modern commentary on Aquinas’s treatment of evil, Brian Davies’s “The Reality of God and the Problem of Evil” is very helpful.