Thomas Aquinas

Thomas refuses innatism and holds, following Aristotle, that all knowledge begins with the senses, the intellect being at first like a blank slate on which nothing is written. But the empiricism is tempered: the agent intellect does not passively receive the sensible, it abstracts from it the intelligible form, drawing the universal out of the perceived particular. Knowledge therefore starts from experience without reducing to it, which keeps Thomas on the empirical side without making him a strict empiricist, the activity of the mind having its irreducible share.

There is nothing in the intellect that was not first in the senses.Disputed Questions on Truth, q. 2, a. 3, arg. 19

Summa Theologiae, Ia, q. 84-85

On the quarrel of universals, Thomas holds a moderate realism that claims to reconcile Plato and Aristotle: the universal exists in three ways, as an idea in the divine intellect before the thing, as a common form in the individuals, and as an abstract concept in our mind after the thing. He thus refuses both the Platonic realism of separate forms and the nominalism that would see in them only names: the universal is really grounded in things, yet exists as a universal only in the intellect that abstracts it.

On Being and Essence (De ente et essentia), 3-4

Thomas gives its classic formula to the correspondence conception: truth is the adequation of thing and intellect, the agreement of thought with what is. But he grounds it theologically: things are true because they conform to the idea God has of them, and our knowledge is true when it is regulated by them. Truth is therefore first in the intellect, divine then human, and the correspondence between mind and the real itself has its origin in God.

Truth is the adequation of thing and intellect.Disputed Questions on Truth, q. 1, a. 1

Disputed Questions on Truth, q. 1, a. 1-2

Taking up Aristotle's eudaimonism, Thomas grants that every action aims at a final end, happiness; but he shows that no finite good, neither wealth, nor honour, nor pleasure, nor even philosophical contemplation, can satisfy the human being's natural desire, which is stilled only in the universal good. Now God alone is that good without limit: perfect beatitude can therefore consist only in the beatific vision, the contemplation of the divine essence, unreachable in this life and received by grace. Greek eudaimonism is thus preserved yet surpassed, the sovereign good being referred to a perfecting that nature calls for without being able to attain it on its own.

Ultimate and perfect beatitude can lie only in the vision of the divine essence.Summa Theologiae, Ia-IIae, q. 3, a. 8

Summa Theologiae, Ia-IIae, q. 1-5

Thomas takes up Aristotelian hylomorphism, every sensible being being a compound of matter and form, but adds a decisive distinction: in every creature, the essence (what the thing is) is really distinct from the esse (the act of existing). An essence does not possess existence of itself, it receives it; in God alone is the essence to exist, he being subsistent being itself. The nature of things is therefore genuinely real and defined, yet radically dependent, hanging on the act of being that God communicates to it. An essentialism, but reordered by the primacy of existence as act.

On Being and Essence (De ente et essentia), 4-5 · Summa Theologiae, Ia, q. 3, a. 4

Against the Platonic dualism that makes the soul a pilot lodged in the body, Thomas holds the soul to be the form of the body in the Aristotelian sense: the human being is not a soul using a body but a substantial unity, a single being whose soul is the formal principle. The self is therefore a substance, but a hylomorphic substance, not a pure spirit. The difficulty proper to Christianity, personal immortality, is resolved by making the human soul a form indeed united to the body yet subsistent, capable of operations (intellection) that do not depend on an organ, and thus able to survive death while awaiting the resurrection.

Summa Theologiae, Ia, q. 75-76

Thomas holds a real free will, which he grounds in the intellect: because the will is moved by the good as reason presents it, and no finite good imposes itself on it absolutely, the human being deliberates and freely chooses among the means. But this freedom is not absolute: the will is necessarily borne toward the good in general, it does not choose itself out of nothing, and above all, without grace, it cannot orient itself toward its supernatural end. Hence a measured libertarian position, articulating the creature's freedom with divine motion rather than opposing them.

Summa Theologiae, Ia, q. 83; Ia-IIae, q. 109-114 (grace)

The meaning of life is for Thomas given, inscribed in a providence that orders every being to its end: the human being is created to know and love God, and all his existence finds its direction in this return toward its origin. A slight constructive part remains, since it falls to each one to cooperate freely with this end through his acts, but the fundamental orientation is neither invented nor absurd, it is received from a willed order.

Summa contra Gentiles, III, 25 and 37

Death separates the soul from the body, but the intellective soul, because it subsists in itself, does not perish: it survives awaiting the resurrection of bodies, where the human being will once again be complete. Death is therefore neither sheer nothingness nor the ultimate horizon, but a passage toward eternal life and, for the just, toward the vision of God. This is a properly Christian immortalism, joining the immortality of the soul to the resurrection of the flesh.

Summa Theologiae, Ia, q. 75, a. 6; Suppl., q. 75

Hope is for Thomas one of the three theological virtues: stretched toward the arduous but possible future good that is beatitude, it relies on the help of divine grace. Far from a lucidity without hope, Christian existence is oriented by the confident expectation of an end that surpasses the powers of nature, which places Thomas at the extreme of the pole of hope.

Summa Theologiae, IIa-IIae, q. 17-22

Moral norms are for Thomas neither variable conventions nor arbitrary divine decrees: they have an objective ground in the natural law, the rational creature's participation in the eternal law by which God orders all things to their end. Every human being has access to it through reason, starting from the first precept "do good and avoid evil", from which the fundamental inclinations follow (to preserve one's life, to live in society, to know the truth). Morality is therefore universal and knowable by all, believers or not, which places Thomas on the side of realist universalism; a slight reservation lies in the fact that the secondary precepts admit of variable determinations according to circumstances.

Summa Theologiae, Ia-IIae, q. 91 and q. 94

The criterion of the right lies for Thomas in virtue, a stable disposition that perfects the agent: he takes up Aristotle's four cardinal virtues (prudence, justice, courage, temperance) and orders them to the final end. But virtue ethics is articulated with the natural law, which supplies the objective rule that prudence applies to the singular case, hence a deontological strand: the virtuous agent is the one whose dispositions agree with the rational order of ends. At the summit, the virtues acquired by habit are crowned by the theological virtues, faith, hope and charity, infused by grace, which orient the human being toward an end that surpasses his nature.

Summa Theologiae, Ia-IIae, q. 55-67; IIa-IIae

Taking up Aristotle's political animal, Thomas holds society to be natural and not born of a pact: the human being is led by his nature to live in community, since alone he can neither provide for his needs nor develop his reason. The city is therefore not an artifice born of fear, as the contractualists will hold, but the fulfilment of an inclination inscribed in human nature and willed by God, ordered to the common good.

On Kingship (De regno), I, 1 · Summa Theologiae, Ia, q. 96, a. 4

The Summa systematizes just war under three conditions: the authority of the sovereign (no private person may declare war), a just cause (punishing a fault, repelling injustice), and a rightful intention (aiming at the good and at peace, not vengeance or greed). Force is not evil in itself: it is an instrument of justice when these conditions are met, like the sword entrusted to public power.

For a war to be just, three things are necessary: the authority of the sovereign, a just cause, and a rightful intention.Summa Theologiae, II-II, q. 40, a. 1

Summa Theologiae, II-II, q. 40 · Summa Theologiae, II-II, q. 64, a. 7 (self-defense, double effect)

Political authority is for Thomas legitimate and natural, since even a state of innocence would have required a direction of the whole toward the common good. But this authority is not absolute: it is bound to serve the common good and remains subject to the natural law; an unjust law, contrary to the good or to the divine law, does not bind in conscience and is no longer a law but a kind of violence. Hence a position favourable to authority, yet bounded by a higher norm that judges it.

Summa Theologiae, Ia-IIae, q. 96, a. 4 (the unjust law)

Taking up Aristotle's equity (epieikeia), Thomas holds that the law, by its generality, can fail in the singular case where its literal application would contradict the legislator's intention and the common good: one must then depart from it to follow what justice and the common good require. The rule is therefore not a letter to be applied mechanically but the expression of a reasonable intention that prudence interprets, which leans toward the spirit against legalism.

Summa Theologiae, IIa-IIae, q. 120 (epieikeia)

Thomas takes up the Aristotelian hierarchy of living beings, the lower creatures being ordered to the use of the human being, alone made in God's image and endowed with an immortal rational soul. Charity is owed to persons, not to beasts, and cruelty toward animals is blameworthy only indirectly, because it hardens the heart. This is a marked anthropocentrism, tempered by the idea that every creature, insofar as it is, is good and reflects its Creator.

Summa contra Gentiles, III, 112

Charity itself is ordered, Thomas argues: we ought to love all human beings, but not all equally, for the order of nature requires that we first help those close to us, parents and fellow citizens, to whom we are more tightly bound. This hierarchy of duties, grounded in real proximity, places Thomas on the side of partialism, without thereby excluding the universality in principle of love of neighbour.

Summa Theologiae, IIa-IIae, q. 26 (the order of charity)

The supreme love is for Thomas charity (caritas), the Latin rendering of agape: a love of benevolence that wills the other's good and descends from God toward the creature rather than rising from lack toward the good, as Platonic eros does. But Thomas gives it a precise and decisive definition: charity is a friendship (amicitia) of the human being with God, Aristotle's very category taken up and transposed: founded on the sharing of beatitude, it supposes, like every friendship, mutual benevolence and a communion. The gift remains primary, since it is God who loves first and makes this friendship possible by grace, yet it takes the reciprocal form of philia, not that of a one-way gift; the old upward thrust of desire toward the good nonetheless persists as a residual share.

Charity is a kind of friendship between man and God.Summa Theologiae, IIa-IIae, q. 23, a. 1

Summa Theologiae, IIa-IIae, q. 23 (charity as friendship)

Can reason and faith contradict each other? Thomas answers no, and his argument rests on a thesis about their shared source: one and the same God is the author of nature, which gives reason its light, and of Revelation; one truth therefore cannot belie another. Against the Averroist doctrine of double truth, which reserved an independent domain for philosophy, he distinguishes without opposing: reason establishes by itself the preambles of faith (the existence of God, the immortality of the soul), while the properly revealed mysteries, such as the Trinity, surpass reason without contradicting it. Where an argument seems to refute the faith, it is because it is badly conducted, and philosophy itself can expose the flaw.

Summa contra Gentiles, I, 3-9 · Summa Theologiae, Ia, q. 1, a. 8

Thomas rejects both fideism, which would treat God's existence as a mere matter of faith, and Anselm's ontological argument, which claimed to deduce it from the concept alone: for a finite mind, God's existence is not self-evident, it is demonstrated from effects. Hence the Five Ways, which all start from a fact of experience (motion, causation, contingency, degrees of perfection, the ordering of ends) and rise, to avoid an infinite regress, to a first term: an unmoved mover, an uncaused cause, a necessary being. Theism is thus held to be rationally established, and not merely believed.

Whatever is moved is moved by another; we must therefore arrive at a first mover moved by nothing, and this everyone understands to be God.Summa Theologiae, Ia, q. 2, a. 3 (the first way)

Summa Theologiae, Ia, q. 2, a. 3 (the Five Ways) · Summa contra Gentiles, I, 13

Thomas inherits Aristotle's four causes and the primacy of the final cause: every agent acts for the sake of an end, and it is this orientation that makes nature intelligible. But he radicalizes finalism by referring it to God: the order of ends observable in the world, which culminates in the fifth way, presupposes an intelligence directing the beings devoid of knowledge toward their goal, as the arrow is directed by the archer. Nature is therefore not a blind mechanism but a willed order, in which each thing tends by its form toward the perfection that belongs to it.

Summa Theologiae, Ia, q. 2, a. 3 (the fifth way); q. 44, a. 4

How can a good God allow evil to exist? Thomas takes from Augustine the thesis that evil is not a thing nor a substance created by God, but a privation, a lack of being or of good that ought to be there, as blindness is the absence of sight. God therefore does not create evil; he permits physical evil for the sake of a greater good in the order of the whole, and moral evil out of respect for free will, without which there would be neither virtue nor merit. The profile thus blends theodicy (evil ordered to the good of the whole) and the free-will defence inherited from Augustine.

Summa Theologiae, Ia, q. 48-49 · Summa contra Gentiles, III, 71

God is for Thomas radically transcendent, distinct from the world he creates out of nothing, and his essence surpasses everything we can conceive: by reason we know of him only what he is not (negative theology). Yet transcendence is not sheer separation, for God is also intimately present to every thing as the cause that gives it being at each instant. This articulation is expressed by the analogy of being: the perfections of creatures (goodness, wisdom) are found in God, but in an eminent degree and in a mode that escapes us, neither purely identical (univocity) nor purely alien (equivocity).

Summa Theologiae, Ia, q. 3 (divine simplicity); q. 13 (the divine names)