Monday, April 23, 2012

Origin of the Five Ways

Entry 0222: Origin of the Five Ways

It is generally accepted that Aquinas's Five Ways of proving the existence of God have their ultimate source in Aristotle. Aquinas is not the originator of the arguments. See for example Leo J. Elders's The Philosophical Theology of St. Thomas Aquinas, (Leiden, The Netherlands: E. J. Brill, 1990), 83-126.

Fergus Kerr offers the following remarks:

“One thing is not always made clear: Aquinas does not regard the Five Ways as his own arguments, nor does he regard them as arguments which might or might not work. Rather, he regards them as arguments that already have worked. In the parallel discussion in the Summa contra gentiles he takes much more time and trouble but even there it is surely plain that he is only rehearsing what he regards as ancient and familiar arguments.

“Admittedly, when Aquinas spells out the First Way, based on the obviousness of change in the world, he does not explicitly refer to Aristotle; but the parallel passage in Summa contra gentiles (I, 13) shows clearly enough that he knows that Aristotle is the source of the argument. The Second and Third Ways, based on efficient causality and the fact that some things have the possibility of being or not being, respectively, have equally clear roots in Aristotle.

“The Fourth Way, invoking degrees of being, goodness, truth, and so forth, the only one in which Aquinas cites Aristotle explicitly, is, paradoxically, as it might seem to us, distinctly Platonist in origin and inspiration. In fact, for all his involvement in the retrieval of Aristotelianism, it has been shown in the last fifty years or so that Aquinas remains profoundly indebted to Platonism.

“No authority is cited for the Fifth Way, from design or teleology, but the brief exposition recalls the most ancient and persistently popular argument of all, dating back to Plato and the Stoics as well as to Aristotle. While of course most of Plato’s texts were unavailable, and there is little sign that Aquinas knew much of the Stoic literature at first hand, it is surely clear that he takes it for granted that he is expounding a very familiar argument.” (1)

(1) Fergus Kerr, “Theology in Philosophy: Revisiting the Five Ways,” International Journal for Philosophy of Religion 50 (2001): 115–130.

Origin of the Five Ways (I)

Concerning the sources of Aquinas’ Five Ways, Leo J. Elders comments that

“The Five Ways of St. Thomas are a summary and transposition into a unified structure and stringent form of more than sixteen hundred years of philosophical efforts to prove God's existence. St. Thomas himself was very much aware of the fact that he was using materials from philosophical tradition.”

More specifically, concerning the First Way, Elders remarks that

“In the First Way Aristotle’s analysis of motion which St. Thomas himself fully endorses is used … St. Thomas’ argument is directly dependent on Aristotle's demonstration of the existence of the First Unmoved Mover.”

Then, considering the First Unmoved Mover, Elders continues,

“It is surprising to see that after Aristotle the argument is seldom used. The idea of a First Mover at the outside of the universe may have held little attraction. The argument was perhaps disregarded by Christians because it was thought to be connected with the theory of an eternal world. However, it made its influence felt inasmuch as it contributed to the general admission of God's total immutability …”

Elder finally concludes his commentary on the sources of the First Way by saying that

“Thomas main sources were the texts in Aristotle’s Physics and Metaphysics.” (1)


(1) Leo J. Elders, The Philosophical Theology of St. Thomas Aquinas, (Leiden, The Netherlands: E. J. Brill, 1990), 90-91 and 95-96.

Origin of the Five Ways (II)

On the sources of Aquinas’ Second Way of demonstrating the existence of God, Leo J. Elders remarks that

“In Summa contra gentiles I, 13 Aquinas seems to ascribe the argument to Aristotle. However, upon closer inspection the text does not say more than that Aristotle shows that in a series of efficient causes infinite regress is not possible and that, therefore, there must be a first.”

Elders then explains that “Aristotle's text is found in Metaph. II (a) 2, 994 a 1ff., where he [Aristotle] sets forth the principle that in a series of causes, whether material, formal, efficient, or final, there must be a first, but it is not used as a demonstration of God's existence. Aristotle could hardly have done so because God is neither a first material nor a first formal cause. In his commentary on the text Aquinas refrains from reading a demonstration of God's existence into these lines.”

Finally, Elders concludes by saying that “Van Steenberghen's statement [in Le probleme de l'existence de Dieu dans les écrits de S. Thomas d'Aquin, Louvain-la-Neuve, 1980, p. 187] that the Second Way is entirely taken from Aristotle must be qualified.” (1)


(1) Leo J. Elders, The Philosophical Theology of St. Thomas Aquinas, (Leiden, The Netherlands: E. J. Brill, 1990), 100.

Origin of the Five Ways (III)

Regarding the Third Way, Leo Elders affirms that for Aquinas the possibility of being and of not being belongs to things on account of their matter. And more specifically regarding the influence of Aristotle, Elders affirms that “The ‘it is impossible that these things always exist’ is a principle given by Aristotle in the De caelo 1 cc. 10-12 and accepted by St. Thomas who even explains it in a subsequent line: ‘for that which can not-be, at some point is not.’ This statement is the central point of the argument: a corruptible thing which would never cease to exist, would have the possibility of not being corrupted, while at the same time it is corruptible. But this is impossible. (See In I De caelo, 1.29, n.283 and 1.26, n.257.)” (1)

Later Elders explains that regarding the influence of Aristotle on the Third Way, “some have pointed out to Metaph. XII 6, 1071 b 22-27 as the source of the argument: What is possible, does not have existence of itself but depends on something in act; of itself a possible being remains in potency; from the point of view of possibility alone at some time nothing is.” And then Elders adds that “More recently scholars have drawn attention to the De caelo I 12, where the statement is found: ‘What can not be, at a certain time is not.’ With this insight Aristotle provided an essential element for the argument as we find it in the Summa theologiae.” (2)


(1) Leo J. Elders, The Philosophical Theology of St. Thomas Aquinas, (Leiden, The Netherlands: E. J. Brill, 1990), 102-103.

(2) Ibid., 107.

Origin of the Five Ways (IV)

Regarding the sources of the Fourth Way, Leo Elders pointed out that “it is remarkable that both in the Summa contra gentiles, I, 13 and in the Summa theologiae, I, 2, 3 as well as in the Quaestio disputata de potentia, 3, 5, Aquinas refers to Aristotle. The texts of the Corpus quoted are Metaph. II 993 b 24 f. and IV 1004 b 2 ff (there are degrees in falsehood, therefore also in truth). The principle formulated by Aristotle has already been discussed in our analysis.”

In the analysis, Elders asks “How can we proceed from the existence of limited perfections to that of an unlimited being?”

And he answers that “St. Thomas has taken over from Aristotle or rather from the Corpus Aristotelicum the principle: ‘That which gives other things a certain form or perfection has itself this perfection to the highest degree.’ However, Aquinas uses the maxim in a different way and states that where a perfection is found according to more or less there must be something which has it most.”

“Although the doctrine of participation is hardly Aristotelian,” Elders continues, “Aristotle nevertheless admits that at the level of efficient causality there is a first and a maximum with regard to qualities. He uses the example of fire as an illustration.”

The footnote attached to this affirmation reads as follows: “Metaph. II (a) 1, 993 b 25: fire is hottest and so it is to other things the cause of their heat. Aristotle presents an argument from the degrees of being in the De philosophia, fr. 16. See De ideis, fr. 3. One may also compare Met. 1055a 3 ff.”

Elders then adds, “Above all Aristotle teaches the unity of being, which to St. Thomas is of paramount importance: the transcendentals coalesce in the unity of the concrete thing and do not constitute juxtaposed distinct formal realities.”

Elders further explains that “The transcendentals are modes of being rendering explicit what is already contained in things. Being shows itself in the perfections it exhibits. For this reason St. Thomas can pass from the transcendental concepts to a conclusion about being. He does so with the help of an argument borrowed from Metaphysics II 1: ‘Things which are truest, are also most being.’ In this chapter Aristotle shows that the highest things, viz. principles and causes, are truest because they are the ground of our knowledge and certitude. St. Thomas changes the order somewhat and argues from truth to being. The argument is valid, for ‘truest’ is that being which also communicates its truth to others. This is what causes do.”

Finally, Elders points out that “In De substantiis separatis (chapter 3) St. Thomas describes Plato’s doctrine of participation and explains to what extent it agrees with Aristotle views.” (1)


(1) Leo J. Elders, The Philosophical Theology of St. Thomas Aquinas, (Leiden, The Netherlands: E. J. Brill, 1990), 113-119.

Origin of the Five Ways (V)

Concerning Aristotle’s influence on the formulation of the Fifth Way, in his The Philosophical Theology of St. Thomas Aquinas, ([Leiden, The Netherlands: E. J. Brill, 1990], 121-125) Leo Elders writes:

“The teleological argument is that proof of God’s existence which is most widely found in religious and philosophical tradition. The reason is that it is obvious to man that order does not come from nothing but requires someone who arranges things.

“In the prologue to the Lectura super Evang. Ioannis St. Thomas calls this the most efficacious way.

“Aristotle gives a version of this proof of God in De philosophia (Fr. 10 R). And in Metaph. XII 10, 1076 a 3 Aristotle attributes to Homer the thesis that there must be one principle which governs the cosmos.

St. Thomas agrees with Aristotle that this teleological organization shows most in animal life (In II Phys., I.13, n.259).

“Against the objection that it is impossible to speak of finality in inanimate bodies, St. Thomas maintains that natural things without knowledge act for an end, because they always act in the same way so as to obtain the best result (‘id quod est optimum’).

“What does Aquinas mean by his statement that these natural things are always or almost always acting in the same way and reach what is best? When we read this text against the background of the commentary on Aristotle’s Physics II, lesson 13 which explicitly studies this question, we notice that to act for an end is distinguished from chance events. What happens by chance is not directed towards a certain purpose. The classic example is that of a tile falling from a roof which hits a pedestrian who happens to be passing.

“It is impossible that things which happen always or in most cases in the same way, come about by chance. (The wording of the first lines of the Fifth Way is very close to Aristotle’s text [Phys. II, c.8] and that of St. Thomas commentary [ibid., n.256]). The reason is that in chance events there is no intended connection between an action and the result obtained. Therefore this result comes about in a capricious manner.

“In the activity of natural things where there is a final term, there is an intended connection between the action itself and its result.

St. Thomas explains this in his already quoted commentary: when something is done naturally in a certain way, it has a natural disposition and aptitude (‘aptum natum est’) to be done in this way (In II Phys., n.257). This is precisely what Aristotle writes himself: ‘and as they are by nature such as to be, so they are done, if there is no impediment’ (Phys., 199 a 10 transl. by W. Charlton).

“What Aristotle writes is obvious: every year in spring the sun climbs higher in the ecliptic, it warms the atmosphere and the higher temperature melts the snow; the chemical elements react with one another according to a set affinity; in the course of the seasons of the year plants act always or almost always in a regular pattern to reach certain ends. They do so according to their natural aptitude. Nature has fitted them out in such a way that these activities follow conveniently and easily. (See In II Phys., I,12, n.252.)”

God's Existence versus God's Actus Essendi 

It is well known that the question “Does God exist?” had an affirmative answer before the time of Saint Thomas Aquinas. The discovery of the notion of actus essendi was not needed to put to rest the issue of God’s existence. The historical path of the philosophical demonstration of the existence of God is the historical path of a judgment of existence applied to God.

The issue of the definition of the essence of God in terms of the metaphysical principle of actus essendi, on the other hand, is not only an issue different from the issue of God’s existence, it is also an issue that took a different historical path in its development. Aquinas was indeed able to express the human intellect’s awareness of the real in the technical terminology of the actus essendi, but there is no question that before the discovery of the notion of actus essendi, answers to the question “Does God exist?” had been given in terms of a judgment of existence.

In his understanding of esse, Aquinas distinguished clearly between the esse that answers the question of existence (the question an sit) and the esse that connotes the metaphysical principle of actus essendi. And here something that may seem obvious needs to be emphasized. After the discovery of the notion of actus essendi, the issue of how to reason and conclude correctly about God’s actus essendi is not to be confused with the issue of how to reason and conclude correctly about God’s existence.

John Haldane on the First and Fifth Ways

In a recent interview, Professor John Haldane was asked: “Aquinas’ famous cosmological argument is partly famous because it has been subjected to huge critical study and would seem to have been rendered obsolete. Haven’t developments in modern logic after Frege left much of Aquinas generally in a mess? Doesn’t too much of the original system – brilliant though it was in the time he was writing – depend on errors that subsequent generations have discovered?”

Professor Haldane answered: “There are several places in Aquinas’ writings where he refers to natural philosophy, i.e. to what we would consider empirical science, and makes statements that we now know to be false. Examples concern human physiology, conception and embryological development, and aspects of physics, chemistry and astronomy. Where these are invoked in arguments, e.g. about sensation, the beginnings of life, or the nature of the heavenly bodies the result may be to render arguments unsound, but the deeper issues are generally metaphysical and the interesting question is whether the arguments can be reformulated in terms of corrected empirical facts, and how far such reformulation takes one away from Aquinas’ central purpose.

“So far as arguing to the existence of God is concerned, Aquinas’ main lines of argument do not depend essentially on particular empirical theories. These are set out in the ‘Five Ways’ presented in the second question of his major work the Summa Theologiae, but there are other arguments elsewhere.

“Let me mention two lines of reasoning one teleological, the other cosmological.

“Aquinas claims that the action of some natural organisms is explicable in terms of the ends towards which they move, even though they lack intelligence. These ends generally confer benefits relevant to the natures of the organisms and hence conduce to their good. If we thought of these agents as choosing the ends then we might think that no further explanation was called for, but if they are incapable of choice then there must be some other explanation of their tendencies towards beneficial states, something external and directional, and from this Aquinas reasons to the idea of a benign designer, saying that this is what we call God (‘et hoc dicimus Deum’).

“There is much that has been said about this kind of argument and it is commonly supposed to have been defeated by the theory of evolution through mutation and natural selection. But evolutionary speciation itself rests on teleologically-structured processes which it does not and cannot explain. There is much more to be said and if readers want to see how this debate might develop they could look at my debate with the late Jack Smart in Atheism and Theism. Here all I want to point out is that the argument neither excludes nor is rendered unsound by evolutionary processes.

“The second argument is that involving essence and existence – and by existence I mean actuality or ‘be-ing’, i.e. existing. In this sense existence is a metaphysical aspect of any existing thing and it is not captured by the existential quantifier.

“Aquinas points out that if we were to inquire into some kind of entity we might ask what is it? i.e. ask about its nature or essence, but also ask is it? does it actually exist? The fact that the second question remains open even when the first has been answered shows that the existence of the thing does not follow from its essence. So if it exists its existence must derive from something else.

“Of that prior source one can again ask whether its existence is implied by its nature and if not then we have to look for a further source, and so it continues. If a vicious regress is to be avoided we must suppose that there is something in which existence is implied by essence and which has the power to confer existence on other things. So again Aquinas is led to the idea of God as the creator, and indeed sustainer of the being as well as of the natures of beings. While this argument may be contested it is a purely metaphysical one and does not rest on particular empirical claims and hence is not refutable by appeal to scientific discoveries.”

The interview was first published by “3:AM Magazine” on Tuesday, 4 December 2012 under the title “Aquinas amongst the Analytics.”

Link to the full interview: