The Fourth Way: Aquinas’ Argument from Gradation

*As with the third way, the fourth way is incredibly and notoriously difficult to understand, and there is significant disagreement amongst Thomists about how best to interpret it. The following is what I perceive to be one of the best interpretations, although I still have some reservations. As such, the following should be considered one possible legitimate interpretation of the fourth way, and not necessarily as an exact or definitive interpretation.

The Argument

  1. Among beings, there are some more and some less good, true, noble, etc.
  2. More and less are predicated of different things, according as they resemble in their different ways something which is the maximum
  3. Therefore, there is something most good, most true, most noble, etc.
  4. Whatever is most good, most true, most noble is also most real (maximum of being)
  5. The maximum in any genus is the cause of all in that genus
  6. Therefore, for all beings there must be something which is the cause of their being, goodness, and every other perfection
  7. This is what we call God

The Defense

The fourth way is an argument from gradation of being, and premise one points out this gradation immediately. This does not just mean that there are different kinds of beings, but that there are different ontological levels of reality. Some things merely exist (rocks, stars, atoms); some things exist and live (bacteria, plants); some things exist, live, and have sense perception (animals); some things exist, live, have sense perception, and reason (humans). Each step adds a qualitatively new, metaphysically higher mode of being. As Saint Thomas would put it, each step has a higher perfection than the previous.

A “perfection” is a specific way in which something is actual. Aquinas writes that “a thing is perfect in proportion to its state of actuality, because we call that perfect which lacks nothing of the mode of its perfection” [1]. The primary perfection of all things is existence, since without existence nothing could be actual at all, or have any other perfections. Saint Thomas states: “Existence is the most perfect of all things, for it is compared to all things as that by which they are made actual; for nothing has actuality except so far as it exists” [2].

The perfections that Saint Thomas refers to in premise one are known as “transcendental” perfections. For Saint Thomas, the transcendentals are properties which “transcend” both species and genus and apply universally to all existing things, albeit analogically. These are properties such as goodness, truth, beauty, nobility, etc. These qualities can be predicated of everything. People are beautiful, but so are mountains and stars and electrons. There can be good people and good food and good books and good pets. They are said to be analogous because what makes a good book is not the same as what makes a good pet. Goodness looks quite different in each; but it is still in some sense really “goodness”.

Transcendental perfections are applicable universally because they are ultimately convertible with being, and being is applicable universally (everything that exists in any way has being). As Aquinas puts its, “goodness and being are really the same, and differ only in idea” [3]. Or as a more contemporary philosopher explains, they are different “in sense but not in reference” [4]. In other words, they refer to the same thing but are viewed from different angles, under different aspects. Goodness is being insofar as it is desirable; truth is being insofar as it is knowable, or insofar as it conforms to the intellect.

The second premise states that “more and less are predicated of different things, according as they resemble in their different ways something which is the maximum.” This is the most controversial and most misunderstood premise in the argument. Commonly, the premise is incorrectly taken to mean something like “we can only judge things to be better or worse because we have an absolute standard by which to compare them.” Whether or not that statement is true, I simply do not think it is what Aquinas is saying here.

To use Richard Dawkins’ counter-example, we don’t need to have knowledge of whatever is maximally smelly to know that one thing smells worse than another; we just need to have the two things that we’re actually comparing. But if there are two things which differ in their degrees of smelliness, then it is necessarily true that one will be actually the “most” smelly. The same is true no matter to what extent we expand the number of smelly things being considered. Among all humans alive on earth at this very moment, there is necessarily one which is the very oldest. This is not to say that the human which is right now the oldest is the absolute oldest who ever has or ever could in theory live; just that among the set of humans right now, it must be that one is the oldest.

In the same way, in a universe of beings which admit of degrees in transcendental perfections, it must be that there is something best, something truest, and something noblest. And it also must be that these are all one and the same being, because, as we’ve said, transcendental perfections are convertible. There is one thing in the universe, then, which is best, truest, noblest, and, accordingly, “realest”, i.e. something which has the most being.

Premise five is that “the maximum in any genus is the cause of all in that genus”. Now, even Saint Thomas points out that this premise understood in an absolute sense is not universally true. After all, humans are the “maximum” in the genus of animals (i.e. the most perfect animals), and yet it is obviously true that humans are not the cause of all other animals. Rather, as philosopher Michael Augros points out, this premise is only true under a certain condition: when the things within a genus necessitate a cause which cannot be outside of that genus [5].

To grasp this, consider an example: suppose you walk into a dark room which is lit by a single lightbulb (but you aren’t aware of the lightbulb yet). You notice that around the room, some spots are brighter than others. You correctly reason that there must be some spot in the room which is in fact the very brightest. Furthermore, since it is a single, closed off room, you know that the source of light must be coming from somewhere within the room. And hence you conclude that wherever the brightest spot in the room is, that is where the source of light will be. And indeed, as you approach the brightest spot, you discover it to be the lightbulb.

In our case, we are dealing with things which are good, true, noble, and real. The first question we must ask is whether such things necessitate a cause; and the answer is undeniably yes. The fact that some property is possessed more and less by different things shows that those things only have the property imperfectly, i.e. by participation, and not through themselves.

Think of it this way: if there is something that is goodness itself, i.e. whose essence is goodness, and hence is good through itself and not through another, then this thing could not ever possibly become more good than it is. For how can there be anything good which is not contained within “goodness itself.” Goodness itself must be the absolute fullness of goodness, such that it cannot lack any possible goodness. For suppose there are two objects, A and B, and one is more good than the other. They cannot both be “goodness itself,” because then there would be no reason to explain how one is more good than the other. So if there are things which are more and less good, we know they are good only imperfectly. They are good by participating in goodness, not by being goodness itself.

And, as Saint Thomas says elsewhere, “What is such by participation . . . and what is imperfect, always requires the pre-existence of something essentially such . . . and perfect” [6]. In short, if something contains a property by participation, it does not have that property as intrinsic to its essence; and hence it must receive (or be caused to have) that property from something other than itself. Hence, when we discover that there are beings good, true, and noble which exist in gradation, we know that they must have a cause. And, just as in our example of the lightbulb where there could not be a source outside the room, if the genus we are examining is “beings,” it is absolutely impossible that the cause will be something outside of the genus. For whatever is outside of the genus of beings is not a being, and hence does not exist.

Therefore, among things which are good, true, and noble, there is something best, truest, and noblest which is the cause of all that else that is good, true, and noble. Since there cannot be an infinite regress of causes (as we’ve demonstrated in previous posts), this cause cannot be something that merely participates in goodness, truth, and nobility, but must itself be these things essentially. There must be something then which is Goodness Itself, Truth Itself, Nobility Itself, and hence Being or Existence Itself.

And this is what we call God.


The set of all numbers is infinite and hence has no actual “maximum.”  Couldn’t the set of all things good, true, and noble be like this as well?

The set of all numbers might have no actual maximum, but whenever you select two numbers to compare, one will necessarily be the most. The same is true no matter how many numbers you add to the set you are comparing. Comparison requires a determinate number and a determinate number will always have a maximum.

Furthermore, since we know that whatever merely participates in goodness, truth, nobility, being requires a cause, and there cannot be an infinite regress of such causes; we know there must be a first cause which is absolute goodness, truth, nobility, and being and hence is the maximum of each.

In the example of the room, could there not be two lightbulbs and hence two brightest spots and two sources of light within the room? Why could it not be the same for things which have more or less goodness, truth, nobility, and being?

In the example of the room, it is admittedly possible for there to be two brightest spots and hence two lightbulbs; just as, in the whole world, it is possible for there to be a “maximum” age which is possessed simultaneously by two different individuals, if they happened to have been born at precisely the same moment. This is because the natures of things like lightbulbs and humans admit of a multiplicity of instantiation. In other words, the one “human” nature can be instantiated in many different individual humans. But a nature that is Being Itself can in principle have only one instantiation. This is because, as we saw in our post on the third way, whatever is pure being is also pure actuality; and (as was shown in our posts on the first two ways) there can only possibly be one thing that can be pure actuality.

Even if there is something which is the maximum of goodness, truth, nobility, and being, and the cause of these perfections in all other things, why think that it is “God”?

Again, the maximum of goodness, truth, nobility, and being must be Goodness Itself, Truth Itself, Nobility Itself, and hence Being Itself. And as we’ve already shown, whatever is Being Itself must be pure act; and whatever is pure act has the following attributes: timelessness, eternality, immateriality, incorporeality, and immutability. These are the traditional attributes of God.



My interpretation of the fourth way draws heavily from, and is extremely indebted to, the interpretation of philosopher Michael Augros in his paper “Twelve Questions About the ‘Fourth Way'” which can be found here:


Thomas Aquinas. Summa Theologiae. I, Q. 2, Art. 3.

Feser, Edward. Aquinas. London: Oneworld Publications, 2009.

C. F. J. Martin. Thomas Aquinas: God and Explanations. Edinburgh University Press, June 30, 1997.

This series of posts on the fourth way from James Chastek:

Rev. Reginald Garrigou-Lagrance O.P. Reality: A Synthesis of Thomistic Thought. Translated by Patrick Cummins O.S.B. Ex Fontibus Co., 2015.

James Capehart. The Fourth Way – Making Sense of the Argument from Gradation. Presentation at the American Maritain Association MeetingFriday, October 12, 2012. Accessed online:

[1]. Thomas Aquinas. Summa Theologiae. Translated by Fr. Laurence Shapcote, O.P. The Aquinas Institute for the Study of Sacred Doctrine, 2012. I, Q. 4, Art. 1.

[2]. Ibid.

[3]. Ibid. I, Q. 5, Art. 1.

[4]. Feser, Edward. Aquinas. London: Oneworld Publications, 2009. Page 33.

[5]. Michael Augros. Twelve Questions About the “Fourth Way.” Page 24. Accessed online:

[6]. Aquinas. ST. I, Q. 79, Art. 4.





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