Thomas Aquinas

The Five Ways

Inspired by Aristotle and Arabic philosophers, the Christian philosopher Aquinas (1225-1274) argued for five logical ways he could prove the existence of God.

Urfan Ul Hassan
October 2023

To see God in the patterns of Nature

Thomas Aquinas (1225-1274) was a Christian philosopher, highly inspired by Aristotle’s ontology. Aquinas’ belonged to a school of thought known as Scholasticism, a school of philosophy that attempted to reconcile religious principles of Christianity with the principles originating in the works of Aristotle and Plato. To truly appreciate and understand Aquinas’ five ways of proving God’s existence, one has to understand the basics of Aristotle’s philosophy.

Before Aquinas, Aristotle’s works had influenced important thinkers in the Islamic Golden Age; philosophers such as Avicenna (Ibn Sina) and Averroes (Ibn Rushd) both interpreted Aristotle, and wrote their own extensive works on philosophy and medicine. Avicenna’s works influenced Aquinas.

Aquinas and Natural Theology 

Divine theology is the study of what is directly revealed by God, such as in holy books. Divine theology provides knowledge about the true essence of God, while natural theology provides arguments for God’s existence through sense perception and intellect. Natural theology is the study of religious beliefs through a scientific lens; one relies upon reason, observations of nature and deduction. Natural theology will avoid superstitious interpretations for phenomenon in the world; the discoveries through science can logically allude to the existence of God.

However, Aquinas pointed out that not anyone can see God in the patterns of nature, regardless of one's efforts as a scientist, or one's intelligence. To see God, something is also required from the individual, and that something is beyond intelligence or cleverness. Aquinas argued that it is the appropriate human character that is necessary to interpret the scientific findings correctly. Aquinas might have argued that God himself helps certain individuals to discover, or see God in the patterns of nature. Thus, how far an individual can seek God is dependent upon his or her character and sincerity.

Problem of language 

Aquinas stated that since God is immaterial and outside of space and time, our language is not adequate in describing God. Human language relies on sense perception, such that it breaks down when attempting to describe something beyond it. Aquinas argued that the use of metaphors or ambiguous language is not good enough when trying to understand God. However, the use of analogies is sufficient since analogies can lead to logical explanations of something, as contrary to metaphors. If we say that God is good, we are saying something that we are not truly able to understand, but we can understand our intention behind such a description by analogy. 

The Five Ways

In his major work, Summa Theologica, Aquinas argued that there are five ways in which God’s existence can be demonstrated:

1: The Unmoved Mover

If something changes, it is because something else caused that change. That something else is itself changing, and is caused to change by something else. This reasoning will inevitably lead infinite regress; the solution to the problem of infinite regress must be that the first cause of change cannot itself be changeable. Aquinas argued that this unmoved mover is what is understood as God.

2: The Uncaused Cause

Can anything create itself? No - that would mean that the thing that created itself existed before it created itself. Everything must have a cause. To avoid the problem of infinite regress, there must exist an uncaused cause, which must be God. Asking “who created God?” would not make sense since an uncaused cause must be outside of time. However, why must it be God? Philosophizing critically on this issue, which any reader should, do you arrive at any other reasonable alternatives than God?

3: Necessity

Some things exist contingently, meaning their existence depends on something else, and some things exist necessarily, meaning they must exist and cannot be any other way. Two multiplied by two is four. This is necessarily true and cannot be any other way. All things in the universe are dependent on something else to exist – they are contingent. The cause of the universe cannot be contingent but necessary; God is the only being that must exist necessarily. See the full argument by the mathematician Gottfried Leibniz.

4: Degree

There are degrees of perfection in things. Fire is the hottest of all things in the world; other things and their distance from the fire (the source) determines how hot they become. Such is God, the supreme/highest in perfection; he causes the level of essence/perfection in all other things. Thus, Aristotle would argue that the philosophical life for humans is the ultimate path to God; thinking, reasoning and contemplating expresses the human soul to its highest potential.

5: Final Cause

All things in nature move toward a goal, even if they are unaware of it themselves. Nothing moves accidentally. However, if something is not aware of its movement, it is not directing itself toward the goal. The aware archer directs the unaware arrow’s destination. In cosmos, God directs everything to its final destination. See Qur'an chapter 64 - all things, including human beings, are travelers.