Aquinas on Evil and the Will: A response to Mackie

Abstract

This article argues that, without being reducible to a version of the Free Will Defence, Aquinas' theodicy and philosophical theology can offer contemporary versions of the Free Will Defence stronger metaphysical and theological foundations from which a response to Mackie's compatibilistic challenge – probably the most serious challenge against this defence – can be derived. Mackie's challenge to the Free Will Defence is the argument that the possibility of evil is not a necessary condition for the existence of free will, for God – if He existed and was omnipotent, omnibenevolent and omniscient – could have and would have created rational and free agents such that they would always freely choose the good. I claim, following Aquinas' hylomorphic ontology, that the creation of such a will is logically impossible as it would require the creation of a will containing naturally and invariably the formality of the universal and perfect good, and so the creation of a will indistinct from God's, which is by nature uncreated.

Introduction

This article will defend, through Saint Thomas Aquinas's philosophical theology, the theist doctrine from the challenge posited by the logical version of the Problem of Evil. Still, its aim is not to provide a final response to The Problem of Evil, nor to solve the debate; rather, to show, in line with recent work by Agustin Echavarría,¹ Kyle Keltz² and others, that, while maintaining its parsimony and cohesion as a reasoned theology, Aquinas's theodicy ³ can effectively offer a novel defence ⁴ to the Problem of Evil that is capable of overcoming contemporary atheist challenges to more recent defences. In this case, Aquinas' philosophical theology will be presented as an answer to Mackie's compatibilist challenge to modern-day Free Will Defences. Mackie's challenge to the Free Will Defence states that the Free Will Defence, which suggests that the origin of evil might be the free will of human and non-human agents and not God's, relies on a false dichotomy as it does not consider the possibility of God creating free agents who, although externally capable of committing evil actions, were internally determined not to do so.

At the same time, the essay tries to add to the work that has been already initiated by neo-Thomists such as Eleonor Stump⁵, M. V. Dougherty⁶ and Agustín Echavarría⁷ by offering a new understanding of Aquinas's theodicy which is centred on the ontological necessity of the possibility of evil for Creation⁸ and the absolute divine necessity of Creation. Although this reading of Aquinas's theodicy has been previously suggested,⁹ it has been so as a mere consequence of his metaphysics, rather than a positive defence against the challenge posited by the Problem of Evil.

Consequently, the essay aims at contributing to two distinct – although complimentary – literatures by, first, providing a novel response to Mackie's challenge and, second, by offering a new reading of Aquinas's theodicy that can serve as a valuable addition to contemporary Thomistic philosophical theology.

In this paper, I will argue that Aquinas's philosophical theology can provide an ontological response to the Problem of Evil that can overcome Mackie's compatibilist challenge by showing that, contrary to what Mackie claims, rational agents' capacity to want to perform evil actions is necessary for the existence of any rational will distinct from God's. The essay will be divided into three sections. The first section will set out the Logical Problem of Evil and describe its consequences. It will also present the general characteristics of the Free Will Defence. The second section will present Mackie's compatibilist counter-argument to the Free Will Defence, which I take to be the most serious challenge against this defence. The final section will argue that Aquinas's philosophical theology can provide a way out of Mackie's criticism by showing, based on his metaphysical conception of God and evil, that the possibility of doing evil is ontologically inherent to Created Free Will.

I. The Logical Problem Of Evil And The Free Will Defence

The Logical Problem of Evil can be non-formally set out as:

• P1. There is a God who is omnipotent, omniscient and wholly good.

• P2. Good is opposed to evil in such a way that a being who is wholly good eliminates evil as far as he can and there are no limits to what an omnipotent being can do, and an omniscient being can know.

• C. There is no evil in the world.

Given that we know there is evil in the world, then:

• ¬ C

• (P1 & P2) → C

• ¬ (P1 & P2)

Meaning that, as the conclusion is empirically falsified and implied by the conjunction of P1 and P2, through modus tollens, at least one of P1 and P2 must be false. And, as P2 is seemingly an analytic truth about God and good, then:

• ¬ P1 or It is not the case that there is a God who is omnipotent, omniscient and wholly good.

This logical version of the Problem of Evil accuses the theist ascription of properties to God of irrationality: God cannot logically be omnipotent, omniscient and omnibenevolent in the light of the evil we witness in the world. Therefore, the argument is not trying to merely show that in fact God does not exist, but rather to argue that there could not in principle (on pain of logical inconsistency) be such a God. The conclusion is, then, the impossibility of his existence and, therefore, its actual inexistence. This means that, even if the deductive Problem of Evil can be placed within the general debate on the existence of God, the arguments of the atheist and the theist are not, here, directly for and against the existence of God, but for and against the possibility of his existence in light of the fact that there is evil in the world. This has been frequently ignored in the literature, where the debate has been taken as a ‘for’ and ‘against’ the existence of God debate, leading to a general reluctance to theological arguments as question-begging. Such arguments, however, may permissibly be central to any theist defence of the possibility of God's existence and, particularly, they are central to the defence put forward in this work.

To refute the atheist challenge, the theist must only prove, by adding extra premises or modifying existing ones (generally P2), that the set of claims that conform to the theist doctrine is not inconsistent with the existence of evil and so that they can (possibly) be simultaneously true. As I see it, the neglection of this distinction has led to the treatment of theological arguments as arguments based on ‘arbitrary suppositions’ that are ‘part of the religious hypothesis which is still in dispute.’¹⁰ Nevertheless and once the debate has been understood to be on the possibility of God's existence and not on His actual existence, even if it is true that relying on, for example, the existence of fallen angels might only provide a possible explanation for the existence of evils, this does not undermine its value as a solution to the inconsistency that the atheist is claiming to exist between evil and the theist doctrine. In technical terms, this means that a defence can form the basis of a successful response to the Problem of Evil. Consequently, the independently necessary and jointly sufficient conditions for a valid theistic explanation of the existence of evil, apart from it solving the inconsistency between God's existence and the existence of evil in the world, are:

1. (i) Possible soundness of its premises: the theist's explanation must have premises that are not empirically falsified (although they do not need to be known to be empirically true or corroborated as Mackie claims)

2. (ii) Logical validity.

The Free Will Defence

Among the possible theist responses to the Problem of Evil, the Free Will Defence arises in analytic philosophy as one of the most popular ones, and, as Mackie concludes, might be ‘the only hope for a reasoned theodicy’.¹¹ This defence tries to, by adding extra premises and modifying P2, show that P1, P2, and the existence of evil in the world (¬ C) can be simultaneously true. The Defence can be set out in three essential claims:

1. (i) Omnipotence is limited by logical possibility (Modifying P2)

2. (ii) An action is free only if it has no set of antecedent sufficient external causes. So, even an omnipotent God cannot make an agent freely do what is right or create free will without the possibility of evil.

3. (iii) Free will (possibly) ¹² outweighs the possibility of evil it entails either because it is in itself a greater good or because it is a necessary condition for a greater good. Therefore, this is a (possible) reason for an omnibenevolent God to choose to Create free agents even if it logically implies the possibility of evil

II. Mackie's Compatibilist Response

In a crucial argumentative move, Mackie points out that the options that the Free Will Defence leaves open for God are not exhaustive. He claims that there is a third possible world in which God made beings such that they always freely choose good.¹³

Mackie accepts that omnipotence is limited by logical possibility and, rejecting determinism, that ‘It would, no doubt, be incoherent to say that God makes men freely choose the good’ because ‘If God had made men choose, that is, forced them to choose one way rather than the other, they would not have been choosing freely’.¹⁴ Nevertheless, he will plead that the possibility of evil entailed by free will is insufficient to explain the evil perceived in the world. He asseverates that even if the possibility of doing evil, in the sense of not being externally constrained to the good, is inherent to free will as the Free Will Defence claims, the actual performance of evil is not entailed by this possibility. The intuition is that to have a genuine possibility of performing evil there is no need to actually perform an evil action at least once, because one can be externally unconstrained and still always act rightly. There is no logical inconsistency, then, in being free, so having the possibility of performing evil, and always refusing to do evil.

Once free will has been shown to be consistent with always choosing to do good, Mackie suggests that ‘God might have made – that is, created – beings, human or not, such that they would always freely choose the good’.¹⁵ By taking a compatibilist approach to free will, he concludes that God could have provided the antecedent sufficient internal conditions for beings to always want to do good without depriving them of the possibility to do evil – i.e. without externally constraining them. This option, so he argues, would not face God with a logically impossible task because what free will implies is the possibility to perform evil, but not the possibility to want to perform evil. Mackie's compatibilist challenge concludes by claiming that, given that creating agents such that they would always freely choose the good was possible for an omnipotent God and desirable to an omnibenevolent one, if God existed, such a world would exist. Hence, the existence of evil in the world implies, through modus tollens, that God does not exist.

In the following section I will show that Aquinas's ontological conception of evil, God and Creation can provide a response to Mackie's compatibilist challenge by proving that the act of creating such impeccable free will is logically impossible.

III. Aquinas's Defence Against The Problem Of Evil

In this section, I will offer Aquinas's philosophical theology as a theist defence against the Problem of Evil that is able to overcome Mackie's compatibilist challenge. It shows that Mackie's compatibilist option was not available to God, given that it involves the logically impossible task of creating what is by nature uncreated. In order to do so I will first provide a brief account of Aquinas's Aristotelian metaphysics that will serve as the essential basis of what I claim is his reply to Mackie's compatibilist challenge. Later, I will derive, from this metaphysical groundwork, four principles from which Aquinas's response to Mackie will naturally flow. The principles are:

1. (i) If something exists, it must either exist potentially or actually, as there is no third state of existence.

2. (ii) Evil is the privation of a due perfection and so its possibility is inherent to beings in potentiality.

3. (iii) God is pure actuality.

4. (iv) Creation has a principle of actuality and a principle of potentiality.

Finally, I will set out Aquinas's argument based on the preceding principles showing how it effectively tackles Mackie's compatibilist challenge.

Aquinas's Aristotelian metaphysics

It is not only advisable, but also methodologically necessary to start by clarifying the meaning of some of the key metaphysical concepts Aquinas uses to develop his response. In Aquinas's metaphysics, as in Aristotle's, the apparent contradiction of something coming into existence from inexistence, and thus of something being and not being simultaneously, is resolved by introducing an hylomorphic ontology. For both philosophers there is not only one way of existing, but two. Things can either and only exist in actuality or in potentiality, or not exist.¹⁶ In his opuscula philosophica and his Quaestiones disputatae, Aquinas clearly defines these two ways of existence:

Existing in actuality implies ‘the primary act of having form’.¹⁷

Form, taken from Aristotelian hylomorphism, is understood as the definition of an object.¹⁸ This is why existing in actuality is the act of having form, meaning of being defined in a certain way and not in any other.

In simpler terms, existing in actuality is existing in such a way that the existing being contains a form that already defines it in a specific way among all the ways in which it could have been. The word form, although sometimes being the shape of the object, must not be taken to mean ‘shape’ but rather some sort of quality that makes the object be what it is. In a house, Aristotle says, it is the way the bricks are ordered,¹⁹ while in humans the form is the rational soul.²⁰ In both cases the form is intimately related with the function of the object. Whereas,

Existing potentially means what has the capacity of existing in actuality but does not exist actually. In Aquinas's terms, what exists potentially is what can be (but is not actually and hence not yet defined in any way).²¹ For both Aquinas and Aristotle, matter is what always exists in potentiality until it receives a given form that provides its definition and actual existence.

Matter, as defined by Aquinas, is “whatever exists potentially”.²²

Something potentially exists if it has the capacity of coming into actual existence upon the fulfilment of a set of conditions, contrary to the inexistence of things that cannot possibly exist. Fire exists potentially in wood. Even if wood is not actually burning, it has the capacity to burn under specific circumstances, while water has not such potential.

The individually necessary and jointly sufficient conditions through which something that potentially exists comes to exist in actuality are known, in Thomistic and Aristotelian metaphysics, as the four causes: the formal cause, the material cause, the efficient cause and the final cause.

The material cause is the capacity of something to come into actual existence, for example, the capacity of wood to burn is the material cause of fire.²³

The efficient cause is, for Aquinas, ‘some active principle or origin, which we call the efficient cause or mover or agent, from which change originates’.²⁴

In the classic example of the statue ²⁵ built out of marble, the material cause is the virgin block of marble, and the efficient cause is the artist that will bring a figure out of the marble. The notion of efficient cause will be essential in understanding Aquinas's conception of God as pure actuality, which he derives from the necessity to have a first efficient cause or mover that sets the world in motion without being itself efficiently caused.

The final cause is that ‘towards which the agent²⁶ tends, called the goal’.²⁷ The agent or active principle, which is the efficient cause of anything, has itself an end at which his action aims, and this end serves as the final cause. The efficient cause must not always be a rational agent conscious of his goal. For Aquinas, any being tends to a natural good, so, for example, fire tries to propagate itself, or trees try to grow upwards.

The formal cause is what will give the thing its actualization and its matter a definition (a form).²⁸

Going back to Aristotle's examples, in a statue, the marble is the material cause, the artist is the efficient cause, the art the artist wants to produce is its final cause, while the shape of the statue – which defines the actual statue – is the formal cause. As this example shows, the formal and final causes of a being are intimately related, as the form is the partial or total actualization of that final cause.

One of the principles that is derived from this metaphysics and that will serve as the keystone of Aquinas's reply to Mackie's challenge is that if something exists, it must either exist potentially or actually, there is no third state of existence. A statue exists potentially within a piece of marble or actually as a decorative object in some place, in both cases the statue is said to exist and in no other case a statue can be said to be existing.

Aquinas's definition of evil

A second derivation of his metaphysics that will lay the foundations for a response to Mackie's challenge is Aquinas's definition of evil. Aquinas states in his Quaestiones disputatae de Malo (QDM) that ‘evil is not something, but rather the privation of a particular good’²⁹ and that it is, precisely, the privation of a due perfection.³⁰ Before unveiling the meaning of this statement, a precautionary note must be introduced straight away. The fact that Aquinas, as well as Augustine,³¹ take evil to be the privation of a good, does not imply that evil is inexistent³² or that its existence, because of its nature, is in some way less reproachable to God. The fact that evil is a privation does not modify its normative status. Hence, Aquinas's definition of evil does not conform in itself a defence against the Problem of Evil and is only an essential part of his defence.

Now, in what sense is evil a privation of something rather than something? And what is meant by a due perfection?

Aquinas starts, in his QDM, by asking whether evil is something (aliquid), meaning a particular being (ens).³³ He concludes that evil is not a being (ens) or thing (aliquid) for two reasons.

Firstly, taking Aristotle's definition of the good as ‘that at which all things aim’,³⁴ he concludes that everything which is a being (ens), given that it has an inclination towards what is good for itself, must have a relationship of conformity and harmony with what is good. This relationship is usually understood as beings having the good as their final cause. If so, and given that evil is never ‘in harmony with the good’ and always ‘opposing to what is good’ and could not aim at any good,³⁵ it follows that evil cannot be an ens or something (aliquid).

Secondly, Aquinas argues that existence (esse) is in-itself desirable because ‘we see that everything, by nature, desires the conservation of its existence and avoids those things which are destructive of it’.³⁶ Hence, if the good is that at which beings aim, and beings aim at preserving their existence, the act of existing is in itself good. It follows from this that evil – being universally opposed to good – is also contrary to existence (esse), as a particular good. Considering that existing is necessary for being something (aliquid), evil, being contrary to existence, cannot be a thing (aliquid).

Nevertheless, Aquinas points out that even if evil is not a being, it is still very real and, in some way, present in the world. So, given that it does not exist itself as a being, it must exist in the good as a sort of quality of beings. Aquinas will argue that evil exists in beings as a sort of non-being or lack of a quality. More precisely, as the privation of a due perfection.³⁷ What Aquinas means by the privation of a due perfection is easily recognizable in the natural order: while blindness is not a being it does exist in some way, and it exists in a being – the eye – as the privation of the perfection of sight. It must be noted that it is the privation of a due perfection and not the privation of any perfection. The table's incapacity of seeing is no evil because that perfection is not part of its potentialities – it is not due to the table to see. Hence, evil can be re-expressed as the impossibility of actualization of a potentiality of a being.

From the above follows that evil can only arise in beings containing some potentiality because one can only be deprived of something that one does not already have. By contrast, in a good which has no potentiality – so is pure actuality – there is a metaphysical impossibility of suffering a privation, due to the fact that such a being contains or is its due perfection: ‘And if there existed any good in pure actuality, without any potentiality, in the way God is, in that good there could exist no evil’.³⁸

This association of the good with the complete actuality of being is what conforms Aquinas's convertibility thesis,³⁹ which will later prove essential in Aquinas's independent derivation of the impeccable goodness of God from His role as the efficient cause of Creation.

An additional distinction must be made between evil and mere potentiality. While potentiality only implies the lack of actualization of a perfection, evil is privatory and so is an incapacity or impossibility to actualize a perfection. As explained by Still and Dahl, ‘evil is privatory insofar as it inhibits [emphasis added] a thing's natural paths’⁴⁰ to the actualization of its due perfection. This distinction can be easily perceived in the cited example of sight. While asleep, even if our perfection of sight is not in actuality, we are not suffering an evil as far as our eyes have still the capacity to actualize that perfection when awake. Different is the case of blindness where there is an incapacity to actualize the perfection that is due to the being – the eye – as its final cause. Thus, existing in potentiality is a necessary condition for suffering evil, and so sufficient for the possibility of evil to exist, but must not be equated with evil.

The next subsection will show, using Aquinas's ways to the existence of God, that Divine Nature is pure actuality. It will be later proved that such a definition of Divine Nature implies that Created Nature necessarily contains some potentiality, which – due to the relationship between evil and potentiality evidenced in this subsection – entails that Creation inherently has the possibility of evil.

God is pure actuality

One of the virtues of Aquinas's philosophical theology, given that it is derived from the metaphysical notions introduced above, is its cohesion and parsimony. Far from tackling questions on the existence of God, morality, or the Problem of Evil individually, he will find an answer to these in the metaphysics he develops independently of the particular questions. In this way, even if the Problem of Evil and the question on the existence of God are, at least for the theist, independent from one another, Aquinas's Quinquae Viae – five ways – will, apart from trying to prove God's existence, provide an understanding of the nature of God that will serve his case against the Problem of Evil. Aquinas's first way is as follows:

Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction of something from potentiality to actuality. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality (…) Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. (…) It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; (…) Therefore, it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.⁴¹

Consequently, if motion is nothing else than the reduction of something from potentiality to actuality,⁴² and God is the first unmoved mover, who is not put in motion and hence is unmoved, God must be pure actuality who moves – as an efficient cause – everything that is in motion without the need of being actualized by a previous actuality. This makes God the primary and pure actuality, the source of all movement as the first (efficient) cause of motion. From His necessary pure actuality follows that God is, meaning that He is solely His form without potentiality and so form is all He is. Therefore, His definition or form is His Being; and ‘this sublime truth Moses was taught by our Lord’.⁴³ God told Moses⁴⁴ and that he ‘shall say to the children of Israel: He who is [emphasis added] has sent me to you’.⁴⁵

From the principle Aristotle uses to explain change, which claims that everything is either in actuality or in potentiality, Aquinas derives – in an awe inducing intellectual work – the essential Nature of God that – independently – converges with the revelations God himself made, in this case, to Moses. The natural proof of God's existence, which is the necessity of a first unmoved mover, evidences God as the pure actuality. This entails that, if God is pure actuality, as matter is that which exists potentially, He is pure form and contains no matter: He is immaterial. Furthermore, if God is nothing but the form fully actualized, given Aquinas's convertibility thesis, God is absolutely Good and, ergo, is at which everything aims.

Creation cannot be pure actuality so it must have some potentiality

Once Divine Nature is defined as pure actuality, the question on Created Nature arises.

In Aquinas's Aristotelian metaphysics, creating means acting as the efficient cause of the actualization of the potential existence of a being. It is logically implied by this definition that it is logically impossible to create something which is already actually existent. This is so because so doing would imply taking something which already exists actually from potentiality into actuality, and this is logically impossible. For me to be the creator of a fire, I need the wood not to be already burning.

Implied in this general principle of creation is that, contrary to God, all created entities are necessarily constituted both by potentiality, given by their material nature, and actuality, found in their form. They are necessarily composed by actuality and potentiality because if God was to create something which was pure actuality, He himself being pure actuality, would have been creating what is already actually existent – Himself – and hence doing what is logically impossible as shown above. So, considering that what is not purely actuality necessarily has some potentiality – because things cannot be but in potentiality or in actuality – it follows that Creation necessarily has some potentiality. This means that Creation is, qua created, necessarily dual-principled.

Aquinas's defence and response to Mackie's compatibilist challenge

Having already introduced Aquinas's conceptions of evil, God and Creation, this subsection will derive, from this metaphysical scaffolding, a defence against the Problem of Evil and show in what way it can avoid criticisms, including Mackie's.

In the first place, if Creation must necessarily have some potentiality, given the definition of evil as a privation of a due perfection and the relationship between evil and potentiality, the possibility of suffering evil becomes inherent to Creation. All finite entities are, consequently, capable of corruption and so Creation, insofar it was created and so is distinct from God's perfect actuality, implies the possibility of the privation of its perfection.

Still, it could be rightly objected that the mere possibility of suffering evil does not explain the actual existence of evil in Creation. The fact that created things and beings are able to suffer the privation of their perfection is, in its own, incapable of accounting for the realization of that possibility. Such an explanation of evil could be claimed to be as insufficient as explaining world hunger through our inherent capacity to be hungry. So, the dual-principled nature of Creation would – as a necessary condition for suffering evil – only account for the possibility of the suffering we perceive in the world.

To counter this objection, attention must be called to the distinction between two types of evils (malum). One is usually referred to as physical evil, the other as moral evil or, for Aquinas, peccatum. Physical evils are the evils passively suffered, such as the evil of blindness, while peccatum – translated as sin – is the evil committed by rational agents.⁴⁶ In communion with contemporary free will defenders, Aquinas will maintain that the origin of the realization of Creation's inherent possibility of evil is to be found in the sins (peccatum) of free rational agents. And God's possible reason behind the creation of free agents, even when it implied the possibility of peccatum, is that free will is a necessary condition for the personal relationship between God and His Creation which outweighs any possible evil.⁴⁷

Aquinas's defence, so stated, is as vulnerable to Mackie's compatibilist challenge as the contemporary Free Will Defence – as stated in section II – is. This is so because even if the possibility of physical evil is inherent to Creation and also free agents cannot logically be externally constrained not to sin, Mackie could still claim that there is no logical inconsistence in God creating agents in such a way that they would be internally sufficiently determined not to sin. By making agents such that by nature they would never want to perform the peccatum they are externally (and necessarily) able to perform, God could have created the world in such a way that it contained free agents, while keeping the world's possibility of evil a mere possibility.

Contrary to contemporary free will defenders, Aquinas would not reject Mackie's challenge by asserting that a free agent whose nature provides the sufficient antecedent conditions for it to invariably choose the good is logically inconceivable. This is so because of the simple – although remarkably ignored – fact that ‘God has a free choice naturally impeccable and confirmed in good’⁴⁸ and so He himself is impeccable, while also free.⁴⁹ Instead, Aquinas offers a response to Mackie via the rejection of an implicit assumption in Mackie's argument. Mackie assumes that if it is coherent for an agent to be free and internally determined to the good, it follows that it must also be logically possible for God to create such an agent. Aquinas would counter that the latter does not follow from the former because the action of creating an impeccable free will requires the creation of pure actuality and, as it has been already shown, creating pure actuality is logically impossible.

Aquinas would be able to put forward this objection to Mackie because, for him, evil understood as peccatum is no different in its genus from evil understood as physical evil. This means that in both cases evil is the privation of a due perfection, but that in the case of peccatum, it is, specifically, the privation of a due perfection of the rational will. So, it is understood as a ‘disorder in the agent's proper action when something is done otherwise than as it should be’.⁵⁰ Peccatum happens when the will is not directed to its final cause or perfection. This perfection at which the will aims Aquinas calls the universal and absolute goodness, that can be taken to be the moral law or the Good. So, in the same way as it was derived from God's pure actual nature that He is incapable of being deprived of any perfection, it can be derived from the definition of peccatum that a will incapable of moving away from its perfection – that is incapable of peccatum – must be purely actualized in its perfection, meaning, that its form must be the universal and perfect good:

A rational nature, accordingly, which is directed to good, taken absolutely, through many different actions, cannot have actions naturally incapable of going astray from good unless it have in it naturally and invariably the formality of the universal and perfect good.⁵¹

This reveals that when Mackie asks God to create free agents that are incapable of wanting to perform evil, i.e., free agents whose nature allows no possibility of peccatum, he is asking for the Creation of a will whose form is absolutely actualized in the universal and perfect good. It must be noted that while Mackie would accept the possibility of evil as meaning that the will is not externally constrained to the good, he does effectively deny the possibility of the will choosing evil actions – i.e. the possibility of peccatum – even if these actions are ‘possible’ in the previous sense.⁵² Therefore, only when the perfection of the will – the universal good – coincides with the will's form is that it cannot possibly choose evil, because only in that case it cannot possibly be deprived of its perfection as the perfection would constitute its form.

Nonetheless, Mackie's proposal encounters a major difficulty. If God is the pure actuality and so ‘in some way containing within itself the perfection of all beings’,⁵³ He also contains the perfection of the will, the universal and perfect good. This means that from the already proven ontological perfection of God as the pure actuality, it can also be derived the perfect moral nature of the Divine Will whose form is the formality of the universal and perfect goodness:

His goodness in some way comprise the various kinds of goodness of all things. Now virtue is a kind of goodness of the virtuous person (…) It follows therefore that the divine goodness contains in its own way all virtues.⁵⁴

A first corollary is that, as anticipated, an impeccable free will – as the one suggested by Mackie – presents per se no logical impossibility in Aquinas's metaphysics, given that the nature of the Divine Will is necessarily impeccable and free – at least in the sense that it is not externally constrained.

Still, a second implication is that if God contains in its form the perfect and universal goodness, due to the logical and ontological impossibility of Creating what is already existent, He could have not created a will containing the formality of the perfect and universal good. The Creation of such a will would have meant the Creation of the Divine Will and so no Creation at all, which theologically implies no personal relationship between God and His Creation – the greatest good for Aquinas. Hence, the Created will, qua created, requires also a principle of potentiality from which the possibility of peccatus inevitably arises. This inherent possibility of peccatus makes the possibility of evil of Creation a real possibility and not a mere possibility insofar the will is not determined by its nature to the good. Thus, Mackie's challenge is sterile as it demands the Creation of a will incapable of peccatus and that implies the Creation of what is already existent: The Divine Will. Whereas the Divine Will, pure actuality and so part of the unmoved mover, is by nature uncreated. It is then concluded that:

God alone is pure act, admitting no admixture of any potentiality, and thus is pure and absolute goodness. But any creature is a particular good, since it has in its very nature the admixture of potentiality, which belongs to it because it is made out of nothing. And hence it is that among rational natures only God has a free choice naturally impeccable and confirmed in good, whereas it is impossible for this natural impeccability to be in a creature because of its being made out of nothing.⁵⁵

Conclusion

In this article, I have argued that Aquinas's defence can make a valuable contribution to the contemporary debate on the Problem of Evil as it is able to overcome Mackie's compatibilist challenge, taken to be the most serious challenge against present-day theist responses to the logical Problem of Evil. I have therefore presented, by bringing together elements from his whole philosophical and theological work, an original understanding of St. Thomas Aquinas's theodicy in a concise and clear manner so that it can become a meaningful object of study for analytic philosophy of religion.

In the first section of the paper, I have introduced the logical version of The Problem of Evil and what is considered to be the strongest response to it – the Free Will Defence – so as to place Aquinas's contribution within the general debate. In the second section, I offered an account of Mackie's compatibilist challenge to the Free Will Defence, which I take to be the most serious challenge against this defence. In the third and final section I, first, introduced Aquinas' Aristotelian metaphysics and his conception of evil, God and Creation. I claimed that these principles imply that the possibility of suffering evil is inherent to the potentiality of Creation. Afterwards, I considered a first objection, which claims that the possibility of suffering evil cannot in its own account for the evil in the world. I dealt with this objection by highlighting Aquinas's distinction between physical evil and moral evil (peccatum) and arguing, in line with contemporary Free Will Defences, that it is the latter that caused the evil perceived in the world. Next, I noted that Aquinas' defence – so expressed – would still be vulnerable to Mackie's objection, which would counter that free agents could have been created in such a way that were incapable of peccatum. In order to show that Aquinas' defence can in fact overcome Mackie's challenge, I initially indicated that peccatum, being indistinct in genus from evil (malum), is the privation of the due perfection of, specifically, the rational will. Consequently, I claimed that a will incapable of the privation of its due perfection (peccatum) must have its perfection purely actualized and so it must be indistinct from the Divine Will. I therefore conclude that Aquinas's defence overcomes Mackie's challenge by proving that God could not have Created a will incapable of peccatum because such a Creation would have implied the creation of what was already existent, and this is logically impossible.