Thomas Aquinas: Faith, Reason, and the Five Ways to God

A calling against the family’s wishes

Thomas Aquinas was born in the castle of Roccasecca, near Naples. The sources disagree on the exact year: Treccani gives “around 1226”, the Stanford Encyclopedia of Philosophy “around 1225”, and the Internet Encyclopedia of Philosophy a range between 1224 and 1226. The safest way to put it is “around 1224-1226”.

At 19 he joined the Dominican order, the Order of Preachers, in Naples. His family objected: the Internet Encyclopedia of Philosophy notes the order was then new and not without controversy, and Treccani confirms the choice ran against his relatives’ wishes. Thomas held to his decision regardless.

Trained by Albert the Great, between Paris and Cologne

After entering the order, Thomas studied under Albert the Great at the University of Paris for three years. In 1248 he was sent to Cologne, still under Albert’s supervision, where he completed his theological training. The Internet Encyclopedia of Philosophy places the Paris years between 1245 and 1248, before the move to Germany.

It was one long apprenticeship, split across two cities: logic and philosophy in Paris, theology in Cologne.

Master in Paris, author of the two Summae

From 1256 to 1259 Thomas held the chair of regent master of theology at the University of Paris: at 32 he was teaching, preaching, and commenting on Scripture. Treccani places the high point of his output during a second stint of teaching in Paris, between 1269 and 1272, after which he moved to Naples, teaching there from the autumn of 1272 until the start of 1274.

These years of teaching, preaching, and academic disputation produced his two major works, the Summa Theologiae and the Summa contra Gentiles. The Stanford Encyclopedia of Philosophy generally treats the Summa Theologiae as the fullest statement of his mature views on each topic it covers; Aquinas himself says in the text that he wrote it for students just beginning theology. Treccani calls its structure systematic to the point of comparing it with the Gothic cathedrals of the era — a judgment from that source, reported here as such.

The Summa contra Gentiles was begun in Paris and finished after 1259. Its first three books, according to the Internet Encyclopedia of Philosophy, were meant by Aquinas as works of natural theology: arguments reason can develop on its own, before turning to revelation.

The Five Ways: proving God through reason

The argument Aquinas is best known for, according to the Internet Encyclopedia of Philosophy, is the Five Ways: five arguments, laid out in the Summa Theologiae, meant to demonstrate God’s existence. Each one closes with a version of the same line, “this is what everyone understands to be God.” The first three, the Stanford Encyclopedia of Philosophy notes, are cosmological arguments resting on the impossibility of an infinite chain of causes.

Way	Starting point	Argument in brief
First	Motion	Whatever moves is always moved by something else; a first, unmoved mover is required
Second	Efficient causation	Nothing causes itself; tracing causes back requires a first cause
Third	Possibility and necessity	Whatever exists contingently points to something that exists necessarily
Fourth	Degrees of perfection	Goodness, truth, and nobility come in degrees; a degree presupposes a maximum
Fifth	The governance of the world	Even things without awareness act toward an end, a sign of an ordering intelligence

Practical example: a billiard ball sits still for a while, then starts moving: someone struck it with a cue, and the cue in turn moved because a hand pushed it. In the first way, Aquinas builds the same kind of chain: everything in motion is moved by something else, and an endless series of pushes still does not explain why anything moves at all. His argument requires a first mover that moves without itself being moved.

The philosophical background behind these arguments sits with Aristotle: cause, act, potency, the vocabulary Aquinas leans on throughout.

Faith and reason, without a real conflict

For Aquinas, in principle, faith and reason cannot genuinely clash. The Stanford Encyclopedia of Philosophy reports that some truths lie beyond human reason’s reach: knowing them requires divine revelation, since Aquinas held them necessary for salvation. A philosopher who reaches conclusions at odds with faith, in his reading, has simply misused philosophy.

Treccani describes this framework as an organic link between theology and philosophy, a methodical partnership between the two disciplines. The same source credits Aquinas with building a Christian Aristotelianism: folding Aristotle’s thought into a Christian theological frame. For the broader scholastic method this project belongs to, see the articles on scholasticism and medieval philosophy; for a comparison with another major theological-philosophical system of the period, see Saint Augustine of Hippo.

The legacy: canonization and Doctor of the Church

Thomas died on 7 March 1274 at the Cistercian abbey of Fossanova, near Terracina, while traveling to the Council of Lyon. According to Treccani, Pope John XXII canonized him in 1323; in 1567 Pope Pius V named him a Doctor of the Church. The two dates, nearly three centuries apart, mark the start of an influence the Catholic Church has recognized formally, each time at its own pace.