mover must formally possess the act it is to communicate to something else if it is to move the latter; it must at least possess it virtually, i.e., have the power to communicate it.) Whatever is moved, therefore, must be moved by something else. One cannot regress to infinity with moved movers, for then there would be no first mover and, consequently, no other mover; for second movers do not move unless they are moved by a first mover. One must, therefore, conclude to the existence of a first mover which is moved by nothing else, and this ‘everyone understands to be God.’ The second way takes as its point of departure an ordering of efficient causes as indicated to us by our investigation of sensible things. By this Thomas means that we perceive in the world of sensible things that certain efficient causes cannot exercise their causal activity unless they are also caused by something else. But nothing can be the efficient cause of itself, since it would then have to be prior to itself. One cannot regress to infinity in ordered efficient causes. In ordered efficient causes, the first is the cause of the intermediary, and the intermediary is the cause of the last whether the intermediary is one or many. Hence if there were no first efficient cause, there would be no intermediary and no last cause. Thomas concludes from this that one must acknowledge the existence of a first efficient cause, ‘which everyone names God.’ The third way consists of two major parts. Some textual variants have complicated the proper interpretation of the first part. In brief, Aquinas appeals to the fact that certain things are subject to generation and corruption to show that they are ‘possible,’ i.e., capable of existing and not existing. Not all things can be of this kind (revised text), for that which has the possibility of not existing at some time does not exist. If, therefore, all things are capable of not existing, at some time there was nothing whatsoever. If that were so, even now there would be nothing, since what does not exist can only begin to exist through something else that exists. Therefore not all beings are capable of existing and not existing. There must be some necessary being. Since such a necessary, i.e., incorruptible, being might still be caused by something else, Thomas adds a second part to the argument. Every necessary being either depends on something else for its necessity or it does not. One cannot regress to infinity in necessary beings that depend on something else for their necessity. Therefore there must be some being that is necessary of itself and that does not depend on another cause for its necessity, i.e., God.
The statement in the first part to the effect that what has the possibility of not existing at some point does not exist has been subject to considerable dispute among commentators. Moreover, even if one grants this and supposes that every individual being is a ‘possible’ and therefore has not existed at some point in the past, it does not easily follow from this that the totality of existing things will also have been nonexistent at some point in the past. Given this, some interpreters prefer to substitute for the third way the more satisfactory versions found in SCG I (ch. 15) and SCG II (ch. 15).
Thomas’s fourth way is based on the varying degrees of perfection we discover among the beings we experience. Some are more or less good, more or less true, more or less noble, etc., than others. But the more and less are said of different things insofar as they approach in varying degrees something that is such to a maximum degree. Therefore there is something that is truest and best and noblest and hence that is also being to the maximum degree. To support this Thomas comments that those things that are true to the maximum degree also enjoy being to the maximum degree; in other words he appeals to the convertibility between being and truth (of being). In the second part of this argument Thomas argues that what is supremely such in a given genus is the cause of all other things in that genus. Therefore there is something that is the cause of being, goodness, etc., for all other beings, and this we call God. Much discussion has centered on Thomas’s claim that the more and less are said of different things insofar as they approach something that is such to the maximum degree. Some find this insufficient to justify the conclusion that a maximum must exist, and would here insert an appeal to efficient causality and his theory of participation. If certan entities share or participate in such a perfection only to a limited degree, they must receive that perfection from something else. While more satisfactory from a philosophical perspective, such an insertion seems to change the argument of the fourth way significantly. The fifth way is based on the way things in the universe are governed. Thomas observes that certain things that lack the ability to know, i.e., natural bodies, act for an end. This follows from the fact that they always or at least usually act in the same way to attain that which is best. For Thomas this indicates that they reach their ends by ‘intention’ and not merely from chance. And this in turn implies that they are directed to their ends by some knowing and intelligent being. Hence some intelligent being exists that orders natural things to their ends. This argument rests on final causality and should not be confused with any based on order and design. Aquinas’s frequently repeated denial that in this life we can know what God is should here be recalled. If we can know that God exists and what he is not, we cannot know what he is (see, e.g., SCG I, c. 30). Even when we apply the names of pure perfections to God, we first discover such perfections in limited fashion in creatures. What the names of such perfections are intended to signify may indeed be free from all imperfection, but every such name carries with it some deficiency in the way in which it signifies. When a name such as ‘goodness’, for instance, is signified abstractly (e.g., ‘God is goodness’), this abstract way of signifying suggests that goodness does not subsist in itself. When such a name is signified concretely (e.g., ‘God is good’), this concrete way of signifying implies some kind of composition between God and his goodness. Hence while such names are to be affirmed of God as regards that which they signify, the way in which they signify is to be denied of him. This final point sets the stage for Thomas to apply his theory of analogy to the divine names. Names of pure perfections such as ‘good’, ‘true’, ‘being’, etc., cannot be applied to God with exactly the same meaning they have when affirmed of creatures (univocally), nor with entirely different meanings (equivocally). Hence they are affirmed of God and of creatures by an analogy based on the relationship that obtains between a creature viewed as an effect and God its uncaused cause. Because some minimum degree of similarity must obtain between any effect and its cause, Thomas is convinced that in some way a caused perfection imitates and participates in God, its uncaused and unparticipated source. Because no caused effect can ever be equal to its uncreated cause, every perfection that we affirm of God is realized in him in a way different from the way we discover it in creatures. This dissimilarity is so great that we can never have quidditative knowledge of God in this life (know what God is). But the similarity is sufficient for us to conclude that what we understand by a perfection such as goodness in creatures is present in God in unrestricted fashion. Even though Thomas’s identification of the kind of analogy to be used in predicating divine names underwent some development, in mature works such as On the Power of God (qu. 7, a. 7), SCG I (c.34), and ST I (qu. 13, a. 5), he identifies this as the analogy of ‘one to another,’ rather than as the analogy of ‘many to one.’ In none of these works does he propose using the analogy of ‘proportionality’ that he had previously defended in On Truth (qu. 2, a. 11).
Theological virtues. While Aquinas is convinced that human reason can arrive at knowledge that God exists and at meaningful predication of the divine names, he does not think the majority of human beings will actually succeed in such an effort (SCG I, c. 4; ST II –IIae, qu. 2, a. 4). Hence he concludes that it was fitting for God to reveal such truths to mankind along with others that purely philosophical inquiry could never discover even in principle. Acceptance of the truth of divine revelation presupposes the gift of the theological virtue of faith in the believer. Faith is an infused virtue by reason of which we accept on God’s authority what he has revealed to us. To believe is an act of the intellect that assents to divine truth as a result of a command on the part of the human will, a will that itself is moved by God through grace (ST II – IIae, qu. 2, a. 9).
For Thomas the theological virtues, having God (the ultimate end) as their object, are prior to all other virtues whether natural or infused. Because the