Edward Feser, Aquinas: A Beginner’s Guide (Oxford: Oneworld, 2009), 104-107.

Let us note first that Aquinas is not in fact trying to argue in the Fourth Way that everything that we observe to exist in degrees (including heat, smelliness, sweetness, etc.) must be traceable to some single maximum standard of perfection. Here (as elsewhere in the Five Ways) his archaic scientific examples have led modern readers to misread him. Given the (false, we now know) medieval theory that fire is the source of all heat, he naturally appeals to fire and heat merely to illustrate the general principle that things that come in degrees point to a maximum. But heat itself is not among the things he is trying here to explain. (This should be obvious when you think about it, since Aquinas would clearly not regard heat or fire as divine attributes!) Rather, he intends to use the principle in question to explain truth, goodness, nobility, being and the like specifically. As the reader may have noticed, this list is very similar to the list of “transcendental” we discussed in chapter 2, which are (unlike heat, smelliness, etc.) above every genus and common to every being, unrestricted to any particular category or individual. And as commentators on the Fourth Way generally recognize, Aquinas is mainly concerned in this argument to show that to the extent that these transcendental features of the world come in degrees, they must be traceable to a maximum. . . . Since Aquinas is not in this argument concerned with heat, cold, sweetness, sourness, fragrance, smelliness, and other mundane features of reality, Dawkins’ objection simply misses the point. Moreover, it should now be clear why Aquinas takes the most true, most good, and most noble being to be one and the same being; for as we saw in chapter 2, Aquinas argues that the transcendentals are “convertible” with one another. That is to say, they are one and the same thing considered under different descriptions. This is also why he draws a related inference that might otherwise seem ungrounded to many modern readers, to the effect that that which is most true, good, and noble is “consequently, something which is uttermost being; for those things that are greatest in truth are greatest in being.” For this follows automatically from the doctrine of the transcendentals.

… Aquinas takes different aspects of reality all to have being in an analogical rather than univocal sense. Accidents and substances both have being, but a substance has independent existence in a way accidents do not; material things and angels both have being, but angels (since they lack matter and are composed of pure form together with an act of existence) are metaphysically simpler than material things and lack the tendency towards corruption that material things possess; created things and God both have being, but in created things essence and existence are distinct and in God they are not. Again, the way in which each has being is analogous to the way others do, but not identical. In particular, it should be evident that substances have a higher degree of being than accidents do, angels a higher degree of being than material things do, and God a higher degree of being than any created thing; for substances lack the dependence on (other) substances that accidents have for their being,angels lack the dependence on matter that material things have for their being, and God depends nothing at all for his existence but is rather that on which everything else depends. We see here a hierarchy in the order of being that dovetails with the hierarchy from prime matter through purely material things, human beings, and angels, up to God as Pure Act that we also had reason to discuss in chapter 2.

Given the convertibility of the transcendentals, it should not be surprising that, just as being does, goodness, truth, and the like come in degrees and are predicated of things analogically. For instance, the goodness or perfection of a triangle drawn carefully on paper with a pen and ruler is greater than that of a triangle drawn hastily in crayon on the cracked plastic seat of a moving bus, for it more perfectly instantiates the form or pattern definitive of triangularity. The goodness or perfection of someone who always tells the truth is greater than that of a habitual liar, for the former sort of person more perfectly fulfills the natural end or final cause of our intellectual and communicative faculties, which is to grasp and convey truth. A triangle and a person are both “good” in an analogical rather than a univocal sense, however, since there is a moral component to human goodness that is absent in the case of triangles and other non-rational entities. Moreover, human beings and triangles, along with other inanimate material things, plants, and non-human animals, manifest different degrees of goodness. Inanimate material things have certain perfections, such as (again) the straightness with which the sides of a triangle might be drawn. Plants, the simplest living things, have these sorts of perfections too given that they are material things, but in addition they have perfections that inanimate things do not have, namely the capacity to take in nutrients, grow, and reproduce themselves. Animals incorporate both the perfections of inanimate material things and plants, but in addition have the capacity for locomotion and sensation, which plants do not have. Human beings possess the perfections that inanimate material things, plants, and other animals have, but in addition have the capacity for intellect and will. Each of these levels of material being represents a higher level of goodness or perfection than the preceding one because it incorporates the perfections of the lower levels while adding perfections of its own. When we get to the purely immaterial levels of the hierarchy of being, we have entities which, though they lack the perfections of material things “formally,” they nevertheless possess them “eminently” insofar as (unlike purely material things on Aquinas’s view) they can grasp them intellectually (and grasp them intellectually in a way that is superior to our way of grasping them, since though the human intellect is immaterial, it is limited because of its dependence on sense organs).

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Return to Lesson 10: The Least Popular of St. Thomas’ Five Ways