(P1)
Among things in the world, we find degrees of perfection: more or less good, true, noble, and beautiful.
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(1) What degrees of perfection means.
- We observe that things around us are not all equally good, equally real, or equally excellent. Some people are wiser, more just, and more loving than others. Some actions are more courageous than others. Some relationships are richer and more genuinely loving than others. Some ways of living seem genuinely fuller and more excellent than others. These comparisons are not arbitrary. They reflect something real about the things being compared.
- When we say that courage is better than cowardice, we are not merely reporting a personal preference the way we might prefer chocolate to vanilla. We are saying something about what courage and cowardice actually are, about the genuine character of these qualities. The Fourth Way begins from this observable fact: reality has a value-structure, and things genuinely differ in how excellently and fully they exist.
(2) The doctrine of the transcendentals: the philosophical engine of the argument.
- Medieval philosophers following Aristotle and drawing on Plato identified a special class of properties called the transcendentals: goodness, truth, beauty, and unity. These are called transcendentals because they are not limited to any particular category of thing. They apply to everything that exists, simply by virtue of its existing.
- Every being, simply by existing, is good to some degree: it has some positive actuality, some real character. Every being is true to some degree: it is what it is and can be known as such. Every being is beautiful to some degree: it has some harmony, integrity, and radiance belonging to what it is. Every being is one: it is a unified thing rather than nothing at all.
- The crucial point is that these properties are convertible with being itself. To say something exists is already to say it is good, true, beautiful, and one in some degree. Degrees of goodness therefore track degrees of being. A more fully actualized being, one with more of its potentials realized and fewer features absent or deficient, is a more fully good being. A being with more unrealized potential, more absence and deficiency, is a less good being.
(3) Why these degrees are objective, not merely matters of preference.
- The Fourth Way does not argue from the contingent fact that human beings happen to prefer some things to others. It argues from the objective structure of reality: things genuinely differ in how fully and richly they exist. A human being has more being than a rock, not because humans happen to value humans more, but because a human being has a richer and more fully actualized mode of existence, with capacities for reason, love, relationship, and self-awareness that a rock simply lacks.
- This claim that degrees of goodness are real features of things, not projections of human attitudes, is philosophically contested. The primary challenges from moral error theory and evolutionary debunking are addressed in Defeaters 4 and 5.
(P2)
Degrees of a transcendental quality are understood by comparison to a real standard that possesses that quality in the fullest way.
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(1) The philosophical theory of participation: its history and meaning.
- The inference from "degrees of perfection exist" to "a real maximum must exist" depends on the philosophical theory of participation. This is not an assumption smuggled in without argument. It is a carefully developed philosophical framework with a long and distinguished history.
- The theory originates with Plato's account of the Form of the Good in the Republic (Book VI). Plato argued that finite things are beautiful, good, and true not because they generate these properties from within themselves but because they participate in transcendent Forms that are beauty itself, goodness itself, and truth itself. Just as visible objects are seen by participating in sunlight, intelligible things are known and are good by participating in the Form of the Good.
- Augustine of Hippo developed this Platonic insight within a Christian framework in the Confessions and City of God: created things are good by participation in God, who is goodness itself and from whom all finite goodness derives. Pseudo-Dionysius the Areopagite, whose Divine Names Aquinas cites extensively, developed the participation framework into a full account of how every perfection found in creation flows from and points back to God as the source of all perfection. Aquinas synthesizes this tradition: the goodness, truth, and beauty found in finite things are real but participated, received rather than self-generated, and their existence in finite things points to a source in which these properties exist not as received but as intrinsic.
(2) Why finite, participated instances require a real source that possesses the property fully.
- A thing that has goodness as something it received, something it did not always possess and could lose, cannot be the ultimate explanation of its own goodness. Something must explain how it came to possess this goodness, communicate it to this thing, and sustain it. That source cannot itself merely have goodness as something received, or the same question arises again. Eventually we must reach a source that possesses goodness not as a received property but as something intrinsic to its nature.
- Think of a heated iron rod. The rod has heat, but the heat is not intrinsic to the iron's nature: the rod received the heat from an external source and will lose it when separated from that source. The rod's heat is a participated instance of heat; it requires a source of heat that is not itself merely receiving heat from something else. Similarly, finite things that possess goodness as something they received and could lose require a source of goodness that does not merely participate in goodness from elsewhere but simply is goodness.
(3) Why this applies specifically to transcendental properties and not to arbitrary scalar predicates.
- The participation inference does not apply to every comparative predicate. There is no maximum existing shoe-size, no real existing maximum of height. The transcendentals are different in kind because they are convertible with being itself. Degrees of goodness track degrees of being, and the maximum of goodness is the maximum of being.
- A very tall thing is not thereby a more fully actual being in any deep sense. But a wiser, more loving, more just being genuinely is more fully actual in the relevant sense: it has more of the properties that constitute a richer and more complete mode of existence. The scale of transcendental goodness is a scale of how fully something exists, and the maximum of this scale is therefore a real metaphysical terminus: the fullest possible mode of existence, which is what the First, Second, and Third Ways identify as purely actual, necessary being. The Fourth Way approaches the same being from the direction of the value-structure of reality.
(IC)
Therefore, if there are degrees of goodness, truth, and beauty in things, there must be something that possesses these perfections in the fullest and most complete way.
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This intermediate conclusion follows directly from P1 and P2. P1 established that degrees of transcendental perfection are real, objective features of the world. P2 established that finite, participated instances of these properties require a real source that possesses them not as something received but as something intrinsic to its nature.
The maximum is not a useful fiction or a conceptual limit we project onto reality for convenience. It is the real, existing source from which every finite instance of goodness, truth, and beauty derives its character. This is an important distinction. Mathematical limits are conceptual tools: the concept of a greatest possible integer is a useful fiction because no such integer exists. But participated goodness is a property that finite things genuinely possess, and genuine possession of a received property requires a genuine source. The maximum is therefore as real as the participated instances that point to it, and in fact more real, because it is their source and explanation rather than a concept derived from them.
P3 below adds the specifically causal dimension: the source does not merely exist maximally but actively communicates its perfections to finite things that participate in them.
(P3)
What possesses a transcendental perfection maximally and intrinsically is the cause and source of that perfection in all things that possess it partially and derivatively.
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(1) The causal principle of participation.
- If finite things possess goodness, truth, and beauty as participated properties, received from a source rather than self-generated, then the source that communicates these properties to them is causally responsible for their having them. A participated property is by definition a received property, and a received property has a giver. The source of participated goodness is therefore not merely the maximum of a scale but the active cause from which finite goodness flows.
- This causal principle follows from the nature of participation itself. It is not an additional assumption added to the argument. If finite goodness is derived goodness, then the source of derivation is a cause of the derived instances. The relationship between the source and the participants is a causal relationship: the source actively communicates the perfection; the participant passively receives it.
(2) Three contemporary analogies replacing the medieval fire illustration.
- Aquinas illustrates this principle with the medieval Aristotelian example that fire, as the hottest thing, causes heat in other things. This example reflects a theory of the four elements that modern chemistry has superseded, and it should not be taken as the philosophical foundation of the argument. The underlying principle is better illustrated by the following examples.
- A teacher who genuinely understands mathematics causes mathematical understanding in students by actively communicating what they know. The students' mathematical knowledge is a participated, derivative instance of the knowledge the teacher possesses more fully and from which theirs is drawn. The students did not generate their understanding from nothing; they received it from a source that possessed it first and communicated it to them.
- A lamp that possesses light causes illumination in the room it shines into. The room's brightness is not something the room generates from its own resources. It is a participated instance of the light the lamp possesses and actively radiates. Remove the lamp and the illumination ceases, because the room's brightness was never its own but always borrowed from the source.
- A supremely good being, one that does not merely have goodness as a received property but simply is goodness itself, would be the ultimate source from which all finite instances of goodness derive their character. Every act of genuine kindness, every instance of real justice, every truly beautiful thing would be, in Aquinas's framework, a participation in the goodness of this ultimate source.
(3) Why the source must possess the perfection intrinsically, not derivately.
- A thing that possesses goodness as a received and derivative property cannot be the ultimate source of that goodness in others. It is itself a receiver, and receivers are not ultimate sources. The lamp illuminates the room, but the lamp's light comes from the electrical current, which comes from the generator, which ultimately depends on some primary energy source. At each level of derivation, we have a transmitter rather than a generator. To end the regress of transmitters we need something that possesses the relevant perfection not as transmitted from elsewhere but as intrinsic to what it is.
- The ultimate source of participated goodness must therefore be a being for whom goodness is not a received property but a constitutive feature of its nature. Such a being does not have goodness; it is goodness. It does not acquire truth; it is truth. It does not participate in beauty; it is beauty. This is Aquinas's description of God as the simple, self-identical source of all perfections: ipsum bonum, ipsum verum, ipsum esse, goodness itself, truth itself, being itself.
(C1)
Therefore, there exists a being that is the maximum and ultimate source of all perfections such as goodness, truth, and beauty found in things.
(C2)
This maximally perfect being, the source of all goodness, truth, and beauty, is what we call God.
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C1 establishes that a being exists which is the maximum and intrinsic source of all transcendental perfections. C2 is not a bare theological assertion. It is the conclusion of a derivation that runs parallel to the derivations in the First Way (C2), Second Way (C2), and Third Way (C3). The key steps follow.
(1) The maximum being is purely actual, with no unrealized potentials.
- A being that is the maximum of all transcendental perfections has no deficiency, no absence of goodness, no unrealized truth, no unactualized beauty. Whatever could make it more fully real, more fully good, more fully true is already actual in it. It possesses the complete fullness of being without limitation or residue. This is precisely what Aquinas means by pure act (actus purus): a being with no unrealized potentials, completely and exhaustively actual in every respect. Every ordinary thing around us has unrealized potentials: a person who could be wiser, a relationship that could be more loving, a creature that could be more beautiful. Only a being with nothing remaining unrealized is the genuine maximum of all perfections.
(2) Pure actuality entails immateriality.
- Matter is precisely the principle of potentiality in physical things: the capacity to take on different forms, states, and configurations. A block of marble is potentially a statue, potentially dust, potentially rubble. This capacity for change and variation, this openness to being otherwise, is inseparable from materiality. A being that is fully actual with no unrealized potentials cannot be material. The maximum being is therefore immaterial, non-spatial, and does not consist of or depend on physical constituents.
(3) Pure actuality entails eternity, necessity, and uniqueness.
- A being that could begin to exist or cease to exist would have the potential for non-existence, which contradicts full actuality. The maximum being therefore exists necessarily and eternally: not merely very long but outside the order of temporal succession entirely, since time is the measure of change and change involves the actualization of potentials, which a purely actual being has none of.
- Two maximally perfect beings would be entirely indistinguishable from each other, since distinction requires one to have something the other lacks, which would mean neither was truly maximal. There is therefore exactly one maximum being. This uniqueness also resolves the challenge posed in Defeater 8: the convertibility of the transcendentals means the maximum of goodness, the maximum of truth, and the maximum of beauty are not three distinct maxima but one and the same fully actual being seen from different angles.
(4) The maximum being possesses intellect and love as intrinsic features of its nature.
- A being that is the fullest source of all truth possesses truth fully. A being that possesses truth fully has complete and perfect self-knowledge and complete knowledge of all that it causes and sustains. Aristotle derived, in Metaphysics XII.9, that the purely actual first cause must be self-thinking intellect: the only activity that is genuinely self-complete and self-sufficient, requiring nothing outside itself to complete it. Aquinas extends this: a being that is the intrinsic source of all goodness is not merely intellectually perfect but is goodness and love in their fullest and most unrestricted form. The maximum of goodness is not a cold abstract principle. It is the fullest possible instance of what goodness means, which includes the rational and volitional character that goodness at its highest always involves.
(5) The Fourth Way is one strand of a cumulative case.
- The Fourth Way alone does not establish every attribute of the God of Scripture or identify this being with any particular religious tradition. The First Way establishes this same being as the source of all actualization of potentials. The Second Way establishes it as the ground of all existence. The Third Way establishes it as the necessary being on which all contingent being depends. The Moral Argument identifies it as the objective standard of moral value. The Fine-Tuning Argument identifies it as a rational designer of extraordinary precision. Historical and revealed theology asks which tradition most accurately describes how this being has acted in human history. The Fourth Way contributes the specific insight that reality's value-structure, its gradations of goodness, truth, and beauty, points to and requires a supreme, perfect, self-identical source of all perfection.
Thomas Aquinas, Summa Theologiae, I, q. 2, a. 3 ("Whether God exists?") – Fourth Way; and I, qq. 3–26 (derivation of divine attributes).
Aristotle, Metaphysics, Book II, trans. W.D. Ross, in The Complete Works of Aristotle, ed. Jonathan Barnes. Princeton: Princeton University Press, 1984.
Plato, Republic, Book VI (Form of the Good and the Sun analogy), trans. G.M.A. Grube, rev. C.D.C. Reeve. Indianapolis: Hackett, 1992.
Pseudo-Dionysius the Areopagite, The Divine Names, trans. Colm Luibheid, in Pseudo-Dionysius: The Complete Works. New York: Paulist Press, 1987.
Augustine of Hippo, Confessions, Books VII and X, trans. Henry Chadwick. Oxford: Oxford University Press, 1991.
Edward Feser, Aquinas: A Beginner's Guide. Oxford: Oneworld, 2009.
Edward Feser, Five Proofs of the Existence of God. San Francisco: Ignatius Press, 2017.
Anthony Kenny, The Five Ways: St. Thomas Aquinas' Proofs of God's Existence. London: Routledge, 1969.
Étienne Gilson, The Christian Philosophy of St. Thomas Aquinas, trans. L.K. Shook. Notre Dame: University of Notre Dame Press, 1956.
W. Norris Clarke, S.J., The One and the Many: A Contemporary Thomistic Metaphysics. Notre Dame: University of Notre Dame Press, 2001.
J.L. Mackie, Ethics: Inventing Right and Wrong. London: Penguin, 1977.
Sharon Street, "A Darwinian Dilemma for Realist Theories of Value," Philosophical Studies 127 (2006): 109–166.
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We can speak meaningfully about "more" or "less" good, true, or noble without there being a real, existing maximum. Comparative language is just a way of ranking things against each other, not a pointer to some supreme existing thing.
1. Comparative judgments about transcendental properties are not mere linguistic conventions.
The objection is most plausible if one treats "better than" as simply a way of expressing a ranking or ordering among things we happen to prefer. On this view, "courage is better than cowardice" means something like "we rank courage above cowardice on a scale we have constructed," and no real maximum is implied because the scale is a human construction.
But this reading fails to capture how we actually use value language at its most serious. When a moral reformer argues that a society's practices are wrong and should change, they are not merely reporting their personal preference or invoking a conventional ranking. They are claiming that the existing practices genuinely fall short of a standard of justice that is real and demanding regardless of whether the society acknowledges it. The claim has the character of reporting something about what justice actually requires, not just expressing a preference. This is the phenomenon philosophers call the objectivity of value, and it is precisely what the transcendentals doctrine attempts to explain.
2. Finite instances of participated goodness require a real source, not a conceptual benchmark.
The Fourth Way does not merely appeal to the logical or grammatical structure of comparative language. It appeals to the metaphysical structure of participated properties. A thing that has goodness as something it received, something it did not always possess and could lose, is not the ultimate explanation of its own goodness. Something must explain how this goodness came to be in this thing, how it is sustained there, and why it exists at all rather than being absent.
This explanation cannot be provided by a conceptual maximum, a merely notional ideal that exists only in thought. A conceptual ideal does not cause anything. The redness of a rose is not explained by the concept of pure redness in someone's mind. The structural harmony of a musical chord is not explained by the abstract idea of perfect harmony. Real participated properties require real causes. The maximum invoked in the Fourth Way is therefore a real causal source, not a conceptual reference point.
3. The alternative view makes finite goodness entirely inexplicable.
If there is no real source of goodness from which finite goods derive their character, then the goodness found in things is either a brute fact with no explanation or a projection of human attitudes with no grounding in reality. Both options are philosophically costly. Brute goodness scattered randomly through the universe with no explanation or source is harder to account for than goodness derived from a real maximum. And the projection view faces the serious problem that our most considered moral judgments do not present themselves as projections: they present themselves as tracking something real about what actions, relationships, and lives are genuinely worth. For the challenge from moral error theory, which denies this objectivity directly, see Defeater 4.
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Even if some properties have a physical maximum, like temperature in theory, this does not mean every quality has a real existing maximum. Abstract properties like goodness or beauty seem to be indefinitely extendable: there is always room for something to be more beautiful or more just. There may be no ceiling.
1. The transcendentals are not arbitrary scalar predicates.
The objection is most forceful against a naive reading of the argument that treats "goodness" like "temperature": a physical quantity with a possible extreme value. Aquinas is not making a claim about a physical extreme. He is making a metaphysical claim about properties that are convertible with being itself.
The transcendentals, goodness, truth, beauty, and unity, are not properties added to a thing from outside. They are aspects of what it means to exist. Every being, simply by existing, is good, true, beautiful, and unified to the degree that it actually and fully exists. Degrees of goodness therefore track degrees of being, meaning degrees of actuality. A more fully actualized being is a more fully good being. An open-ended regress of greater goodness would imply an open-ended regress of greater actuality.
2. The question is not whether the scale has a highest numeral but whether being itself has a maximum.
The real question posed by the Fourth Way is: is there a mode of existence that is fully, completely, and without limitation actual? Is there a being with no unrealized potentials, no absent perfections, no deficiencies of any kind? If so, that being is the maximum not merely of one quality but of all transcendental properties simultaneously, because they are all aspects of the same fullness of being.
The First Way, Second Way, and Third Way each independently establish the existence of a being that is purely actual, the ultimate source of actualization, the uncaused cause of all existence, and the necessarily existing ground of all contingent being. The Fourth Way converges on this same being from a different starting point: the value-structure of reality also points to a purely actual, fully real maximum. The Fourth Way does not need to independently establish that such a maximum exists; it needs to show that the value-structure of reality is additional evidence pointing to the being already established by the other Ways.
3. What is true of partial goodness in caused things points to its source.
Consider that in every finite thing we encounter, the goodness present is clearly incomplete, limited, and capable of being greater. A kind action is genuinely good but clearly not the fullness of goodness. A beautiful piece of music is genuinely beautiful but does not exhaust what beauty can be. This characteristic of finite goodness, that it is always real but always partial, is precisely what the participation framework predicts: things have as much goodness as they participate in from their source, and no finite thing participates in the source fully. The partial character of finite goodness is therefore evidence of its participated, derivative nature, which in turn is evidence of a source that possesses it without limitation.
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This looks like a disguised ontological argument: moving from the concept of maximal goodness or perfection to the conclusion that a maximally good being exists. The ontological argument has been widely criticized, so if the Fourth Way relies on the same move, it shares those criticisms.
1. The Fourth Way and the ontological argument begin from entirely different starting points.
The ontological argument, in both Anselm's original formulation and Plantinga's modal reconstruction, begins from the concept of a maximally great being or the concept of that than which nothing greater can be conceived. It moves from a purely conceptual starting point, a definition or modal intuition, to the conclusion that such a being must exist.
The Fourth Way begins from an empirical observation: we actually encounter things that are more or less good, more or less true, more or less beautiful. This is not a conceptual claim. It is an observation about the world we find ourselves in. Courage really does exist and really is better than cowardice. Acts of genuine love really do occur and really are good. The starting point is the observed, experienced value-structure of reality, not a concept in the mind.
2. The Fourth Way reasons from real effects to a real cause, not from concept to existence.
The ontological argument's critical move is the inference from possibility or conceivability to actual existence. This is what makes it an a priori argument and what makes it philosophically controversial: can we reason from pure thought to existence?
The Fourth Way's critical move is entirely different. It reasons from real, observed instances of participated goodness to the cause that communicates goodness to those instances. This is an a posteriori, causal inference: given that these real things have these real properties in a derived and participated way, what must their source be like? This is the same kind of reasoning a scientist uses when inferring the properties of a cause from the observed properties of its effects. It is inductive and empirical in structure, not conceptual and deductive.
3. The two arguments are complementary, not redundant.
Because the Fourth Way is a posteriori and the ontological argument is a priori, they approach the same conclusion from entirely different directions. If both are sound, they provide mutually reinforcing and independent lines of evidence. The ontological argument, addressed fully elsewhere on this site, shows that if a maximally great being is possible, it necessarily exists. The Fourth Way shows that the observed gradations of goodness, truth, and beauty in the world constitute evidence of a real maximum source. These are different arguments, with different premises and different methods, that converge on a shared conclusion.
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Even if there is a maximally perfect source of goodness and truth, this does not show that it is the personal God of Christianity. It might be an abstract Platonic Form, an impersonal principle, or some force entirely unlike the God of Scripture.
1. This is correct, and it is not what the Fourth Way alone claims to establish.
The argument is designed to establish one specific conclusion: that there exists a real, maximum source of all transcendental perfections, a being that possesses goodness, truth, and beauty not as received properties but as intrinsic features of its nature, and from which all finite instances of these properties derive. That is its contribution. Identifying this being with the full character of the God of Scripture requires further argument, which Aquinas himself provides and which other arguments on this site supply.
2. What the conclusion already establishes and rules out.
The conclusion is not theologically thin. It immediately eliminates several significant alternatives. Atheism and robust naturalism are ruled out, because the intrinsic source of all goodness and truth cannot be the value-neutral physical universe. Abstract Platonic Forms, while a possible stopping point for someone in the Platonic tradition, fail a crucial test: abstract objects are causally inert. A Form does not cause anything. The source the Fourth Way requires must not merely exemplify goodness maximally but actively communicate it to finite things. A causally inert abstraction cannot fill this role, as explained in the Third Way's Defeater 6.
3. The derivation from maximum goodness to intellect and personhood follows from pure actuality.
A being that possesses truth in the fullest way possesses complete self-knowledge and complete knowledge of all it causes. A being that possesses goodness in the fullest way possesses complete rational and volitional goodness, since goodness at its highest is not a mere property of things but the character of a rational, loving will. Aristotle argued in Metaphysics XII.9 that the purely actual first cause must be self-thinking intellect: the only fully self-complete activity is thought thinking itself. The maximum of all perfections is therefore not an impersonal force or abstract principle. It is intellect and love in their fullest and most unrestricted form.
4. The Fourth Way is one strand of a cumulative case.
The First Way establishes this being as the source of all actualization. The Second Way establishes it as the ground of all efficient causation. The Third Way establishes it as the necessary being from which all contingent beings depend. The Moral Argument identifies it as the objective standard of goodness and moral obligation. The Fine-Tuning Argument identifies it as a rational designer of extraordinary precision. Historical and revealed theology then asks which tradition most accurately describes how this being has acted in human history. The Fourth Way contributes the specific insight that reality's value-structure points to a supreme, perfect, personally good source of all goodness, truth, and beauty.
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Philosopher J.L. Mackie argued in Ethics: Inventing Right and Wrong (1977) that moral and evaluative properties are not real features of the world. They are projections of human attitudes onto a value-neutral reality. When we say one thing is better than another, we are expressing a preference or an emotional response, not reporting a fact about the world. If Mackie is right, P1 is simply false: there are no real degrees of perfection out there to explain, and the Fourth Way has no starting point.
1. Mackie's error theory, stated precisely.
In Ethics: Inventing Right and Wrong (Penguin, 1977), Mackie argues that ordinary moral discourse makes implicit claims about objective values, claims that would be true only if there were real value properties in the world. But Mackie contends that there are no such properties: the world as described by science is value-neutral, containing only facts about matter, energy, and physical processes. Therefore, all moral and evaluative judgments are systematically false or empty. We project values onto reality; we do not perceive them there.
2. The error theory is self-undermining when applied consistently.
Mackie's argument is offered as a philosophical claim that is true and that we ought to accept on the basis of evidence and reasoning. But "ought to accept" is itself a normative claim. If value properties are not real features of the world, then the claim that we ought to accept Mackie's argument is itself a projection of an attitude rather than a reporting of a fact. Mackie cannot consistently assert that his error theory is the correct view without invoking the very kind of normative claim his theory declares to be empty.
Furthermore, Mackie's argument relies on the claim that certain philosophical and scientific considerations provide good reasons for his conclusion. But "good reasons" is itself an evaluative concept. If the error theory eliminates all real evaluative properties, it eliminates the property of being a good reason, which means Mackie has no good reasons for his position, only causal factors that produced his belief. The error theory dissolves the grounds for accepting itself.
3. The phenomenology of moral experience resists the projection account.
When we encounter a genuine act of cruelty toward an innocent person, the wrongness of that act does not present itself to us as a feeling we are projecting onto a neutral event. It presents itself as a feature of what is happening: this is wrong, not merely "I feel bad about this." The distinction is important. If someone says "I feel nauseated" they are reporting an inner state. If someone says "that was wrong" in the same tone, they are making a claim about the act itself. The grammar of moral language, and more importantly the experience of moral perception, has the structure of reporting rather than projecting.
4. The Fourth Way's claim is more modest than the full objectivity of all moral judgments.
The Fourth Way does not require that every moral intuition be infallible or that every value judgment be objectively true. It requires only that the transcendental properties, goodness, truth, beauty, and unity, which track degrees of being and actuality, are real features of the world rather than projections. This is a more defensible claim than the full objectivity of every moral norm. That some things are more fully actual, more fully real, more fully integrated and harmonious than others is an observation about the structure of being itself, not merely a moral intuition about which actions to prefer. The challenge to this more modest claim is correspondingly harder to sustain.
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Philosopher Anthony Kenny and others argue that comparative judgments, "A is better than B," do not require a real existing maximum to be meaningful. They require only a shared scale of measurement. Temperature comparisons work without a hottest existing thing. Length comparisons work without a longest existing thing. Moral comparisons similarly require only a shared evaluative scale, not a real maximum of goodness in existence. The inference from "degrees exist" to "a real maximum must exist" simply does not follow.
1. Kenny's objection, stated fairly.
Anthony Kenny, in The Five Ways (Routledge, 1969), presses this point against P2 directly. The objection notes that many comparative scales are perfectly intelligible without a real existing maximum at their top. We can rank things by temperature without there being a hottest existing thing. We can rank things by length without there being a longest existing object. Comparative language does not logically require a real terminus at the top of the scale. Why should it be different for goodness?
2. The transcendentals are not scalar predicates of the ordinary kind.
Kenny's objection succeeds against a naive reading of the argument that treats goodness like a physical measurable quantity such as temperature or length. But this is precisely the reading the Fourth Way should not be given, as explained in Defeater 1. The transcendentals are convertible with being itself. Degrees of goodness track degrees of actuality: how fully a being has realized its potential, how completely it exists. This is not a conventional scale constructed by human measurement. It is a feature of the metaphysical structure of reality.
3. When the scale tracks something real, the maximum has a different status.
Consider two different kinds of scale. A scale for ranking chess players is a conventional construct: Elo ratings are numbers assigned by a system humans invented, and the question of whether there is a "real" maximum Elo rating has no metaphysical force. But a scale for measuring actual temperature, understood as mean kinetic energy of particles, tracks something real. The maximum of this scale, absolute zero, is a genuine physical limit grounded in the nature of kinetic energy itself.
The transcendental scale is of the second kind. It tracks degrees of actuality, which are real metaphysical features of things. The question is then: is there a maximum of actuality? Is there a being with no unrealized potentials, no absent perfections, no deficiencies? The First, Second, and Third Ways argue independently that there is: the purely actual, necessary, uncaused ground of all being. The Fourth Way adds that this same maximum is also the maximum of all transcendental properties, because these properties track actuality and the maximum actuality is their maximum too.
4. Kenny's objection points to what the Fourth Way needs: the participation framework.
Kenny's critique is valuable because it identifies exactly what the Fourth Way needs to establish in order to succeed: not merely that a maximum is conceivable, but that the participated, derivative character of finite goodness requires a real causal source. This is precisely what the participation framework (explained in P2) provides. Finite goodness is not merely a position on a conventional scale. It is a real property that things genuinely possess as something received from outside themselves. A received property requires a giver. The giver must possess the property not as received but as intrinsic. Kenny's objection is a helpful sharpening of what the argument must demonstrate, and the participation framework is the demonstration.
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Philosopher Sharon Street and others argue that evolutionary pressures fully explain our evaluative judgments without any need to postulate real value properties in the world. Natural selection shaped our ancestors to value what enhanced fitness: kin, cooperation, food, safety. Our sense that some things are genuinely better than others is an artifact of this selection history, not a perception of real degrees of goodness in reality. P1 therefore establishes only that we perceive degrees of perfection, not that real degrees exist.
1. Street's Darwinian dilemma, stated carefully.
In "A Darwinian Dilemma for Realist Theories of Value" (Philosophical Studies, 2006), Sharon Street argues that if value realism is true and there are real evaluative facts, natural selection would have had to track those facts to produce our evaluative intuitions. But there is no plausible mechanism by which selection could have tracked abstract evaluative facts rather than simply selecting for behaviors that enhanced fitness. Therefore, our evaluative intuitions are better explained as fitness-tracking responses than as perceptions of real values. The apparent objectivity of our moral experience is an evolved illusion.
2. The evolutionary explanation applies most forcefully to specific survival-relevant intuitions, not to the transcendentals.
Street's debunking argument is most plausible when applied to specific moral preferences that are clearly fitness-relevant: caring for one's children, cooperating with allies, avoiding deadly threats, reciprocating favors. For these, a story about how natural selection produced these tendencies without tracking objective moral facts is at least initially plausible.
But the Fourth Way's P1 does not primarily rest on specific moral preferences or emotional responses. It rests on the observation that things genuinely differ in how fully and richly they exist, that some modes of being are more actualized than others. This is an observation about the metaphysical structure of reality, not a survival preference. The recognition that a rational being has more actuality than a stone, or that a fully functional relationship has more unity than a dysfunctional one, is not the kind of preference that has an obvious fitness-based explanation. It is closer to a philosophical recognition than a survival instinct.
3. The evolutionary debunking argument is self-undermining when applied consistently.
If our cognitive faculties are shaped by evolution to track fitness rather than truth, then the faculties we use to evaluate philosophical arguments, including Street's own argument, are equally products of evolution and equally suspect. An argument that, if successful, gives us reason to doubt all our faculties for evaluating arguments is an argument that saws off the branch it is sitting on. For a full treatment of this self-undermining feature of evolutionary debunking arguments applied to all cognitive faculties, see the Evolutionary Argument Against Naturalism (EAAN) on this site, which addresses this challenge in comprehensive detail.
4. The existence of reliable moral perception is better explained by theism than by naturalism.
If there are real degrees of goodness, truth, and beauty in the world, a theistic framework provides a natural explanation for why our faculties can perceive them: we were created by a being who is goodness and truth itself, with minds designed to know and respond to these realities. On naturalism, the convergence of our evolved perceptual faculties with real objective value properties would be an extraordinary coincidence with no explanation. The reliability of our perception of value is therefore additional evidence in favor of a theistic rather than a naturalistic worldview.
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The inference from "degrees of goodness exist" to "a real maximum of goodness must exist" depends on the Platonic theory of participation, which is itself a deeply contested philosophical framework. Why should we accept that finite things possess goodness by participating in a transcendent source? Why not say instead that finite things are good by virtue of their own internal properties, their functional success, their complexity, or their relational harmony, without any need to derive these properties from an external maximum?
1. The objection is the most philosophically precise challenge to P2 and deserves a direct response.
The participation framework is indeed a substantive philosophical commitment, not a logical tautology. The objection asks: why cannot a thing simply be good by virtue of what it is, intrinsically, without deriving its goodness from any external source? This is a genuine question and the Fourth Way must answer it rather than assume it away.
2. A property that is received rather than intrinsic requires a cause.
The key observation is that the goodness found in finite things has all the marks of a received, not an intrinsic, property. Finite things come to have goodness, develop it, lose it, possess it in varying degrees, and their goodness depends on conditions that could have been otherwise. A human being who grows in wisdom and love becomes more good; one who squanders their capacities becomes less good. The goodness is not fixed and necessary but variable and contingent.
A property that a thing comes to have, that it can gain or lose, that depends on external conditions, is precisely a received property. It was not always there; something brought it about. It may not always remain; something could take it away. Its presence is contingent on factors outside the thing itself. This is exactly the profile of a participated property: something possessed derivatively rather than intrinsically.
3. A thing whose goodness is entirely internal and intrinsic would need to be necessary and self-subsistent.
Suppose a finite thing's goodness were truly its own intrinsic property, requiring nothing outside itself. In that case, the thing could not fail to have this goodness; it would be as intrinsic to its nature as triangularity is to a triangle. But finite things manifestly can fail to have goodness, can develop it and lose it, can have more or less of it. Their goodness is therefore not intrinsic in the relevant sense.
The only kind of being for which goodness would be genuinely intrinsic, not received and not losable, is a being whose very nature just is goodness: a being that does not have goodness but is goodness. Such a being would exist necessarily, would be immutable, and would be the source of all derived goodness rather than an instance of it. This is precisely the terminus the Fourth Way is arguing for. The participation framework therefore does not merely assume what it needs to prove. It follows from careful reflection on the character of goodness as we actually find it in finite things.
4. The alternative view generates an explanatory regress.
If finite things are good entirely by virtue of their own internal properties, with no derivation from any external source, then the goodness of the universe is a brute mosaic of unconnected, intrinsically good things with no common source or ground. This is not merely metaphysically untidy. It is explanatorily impoverished. Why do finite things have the specific degrees of goodness they have rather than others? Why is there any goodness at all in the universe rather than pure value-neutrality? The participation framework answers these questions by pointing to a source; the alternative view can only treat the existence and distribution of goodness as brute, unexplained facts. Between these two options, the participation framework is the more explanatorily powerful position.
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Even if a maximum of each perfection exists, why must all maxima be unified in a single being? Perhaps the maximum of goodness, the maximum of truth, and the maximum of power are distinct entities, giving a plurality of divine principles rather than one God. The argument establishes at most that some maxima exist, not that they are all the same being.
1. The objection has genuine force against a naive version of the argument.
If the Fourth Way simply collected together several separate scales (a goodness scale, a truth scale, a beauty scale) and inferred a maximum of each independently, there would be no obvious reason why these maxima must coincide in a single being. Polytheistic mythologies imagined different divine beings as supreme in different domains: one god of wisdom, another of power, another of love. The objection asks: why does the Fourth Way's conclusion not similarly distribute the maxima among different divine beings?
2. The convertibility of the transcendentals unifies the maxima.
The answer lies in the doctrine of the convertibility of the transcendentals, explained in P1 and P2. Goodness, truth, beauty, and unity are not independent properties that happen to co-occur in some things. They are all aspects of the same underlying reality: the degree to which a being is fully actual. A being that is maximally actual is thereby maximally good, maximally true, maximally beautiful, and maximally one, not because these properties happened to be bundled together by chance but because they all follow from the same underlying fact of full actuality.
The maximum of goodness and the maximum of truth and the maximum of beauty are therefore not three separate maxima requiring three separate beings. They are three descriptions of the same maximum reality: the being that is fully actual, completely real, with no unrealized potential and no absent perfection.
3. Two maximally actual beings would be indistinguishable and therefore identical.
For two beings to be numerically distinct, one must have something the other lacks. If both are fully actual with no unrealized potentials and no absent perfections, neither can have anything the other lacks. Two fully actual beings are therefore indistinguishable in every respect, which means they are not two beings at all but one. This is the uniqueness argument established in the derivation of divine attributes in the Third Way (C3) and repeated in C2 above. It applies here with equal force: there is exactly one maximum being, and all the transcendental maxima coincide in it.
4. This convergence is not an accident but a metaphysical necessity.
The unity of the maxima is not something that needs to be established by a separate argument after the Fourth Way has concluded. It is built into the structure of the transcendentals themselves. Because goodness, truth, and beauty all track the same underlying reality, namely the degree to which something is fully actual, they must all reach their maximum in the same fully actual being. The plurality of maxima problem dissolves once the convertibility of the transcendentals is properly understood.
