The Existence and Essence of God: A Thomistic Perspective
II. The Existence of God
II.1. The Problem of Demonstration
We might think that while God is not perceptible to the senses, He can be perceived by reason. Examples of this type of knowledge are “men are rational animals” or “triangles have three sides”. St. Thomas Aquinas called these propositions self-evident, meaning that the essence of the objects in question is the property referred to in the proposition (the predicate is included in the subject). The examples above are evident to us because we grasp them as real just by understanding the subject concept.
If God’s existence were an essential feature, included in His essence, then we might suppose that the proposition “God exists” could be proven true simply by understanding the term “God.” Some philosophers (St. Anselm and Descartes) believed they could demonstrate God’s existence based on this assumption (the ontological argument).
However, St. Thomas Aquinas argued against this kind of argument because God’s essence is not as clearly given to us as, say, the essence of a triangle. This means the proposition “God exists” is not self-evident to us, even if existence is included in God’s essence.
The Five Ways
The Five Ways. St. Thomas Aquinas stated that it is possible to demonstrate God’s existence. A purely rational argument is inadequate because it doesn’t align with human faculties. We must approach God as known to us through sensory experience. Aquinas’s proofs (Five Ways) are a posteriori demonstrations: they start from the effects of God’s action in the world to trace back to Him as the ultimate cause.
While these proofs don’t grant exhaustive knowledge of God’s essence—impossible given our nature’s limitations—they provide a rational basis for believing in His existence. These arguments have precedents in other philosophers, particularly Aristotle and Plato, and all follow a similar pattern:
- The starting point is a real fact of experience, observing various aspects of the physical world.
- Introducing a metaphysical principle (e.g., nothing can cause itself, the perfect cannot be caused by something less perfect).
- Stating that a causal series cannot proceed indefinitely but must stop at a final term.
- Concluding the necessity of a supreme, transcendent being.
The first way observes motion and affirms God as the Unmoved Mover. The second considers causes in the world and concludes there must be an uncaused Cause. The fourth notes differences in beings’ perfection and proposes a perfect being. The most interesting are the third and fifth ways.
The Third Way highlights the contingency of finite objects: all beings exist but might not exist; they have their features but might not have them. If they might not exist, and it’s unthinkable that at one time nothing existed, then nothing would exist now. Since this isn’t the case, there must be a necessary being, whose reason for existence lies within itself, and that being is God.
The Fifth Way considers the order in the natural world and the need for intelligence to direct beings with end-directed behavior. Since natural beings lack intelligence, they must have been created by an intelligent being who designed their behavior to meet their purposes. Therefore, there must be an ordering intelligence, which we call God.
III. The Essence of God
One of St. Thomas Aquinas’s main challenges was defending the possibility of knowing God without diminishing His being. He maintained a balance, avoiding two extremes: anthropomorphizing God by bringing Him too close to worldly things, and denying the possibility of knowledge by separating Him radically from the world.
Aquinas used several strategies: affirming only properties that don’t imply imperfection, and denying God properties of creatures that imply imperfection. Thus, God is motionless, pure act, immutable, and simple. Eminence means God possesses infinitely the perfections found in creatures, like kindness, intelligence, and will.
Analogy reminds us that words used to describe God don’t have the same meaning as when applied to finite things. They are neither univocal nor equivocal, but analogical, partly similar and partly different.
The Five Ways provide predicates for God: Unmoved Mover, Uncaused Cause, Necessary Being, Most Perfect Being, and Supreme Intelligence. The formal establishment is the fundamental attribute that, according to our way of knowing, is ontologically first and from which all others derive. God’s formal establishment is subsisting being itself: in Him, essence is identical to existence. This property is the root of all other perfections and distinguishes His essence from creatures, where essence and existence differ.
Divine attributes stem from the formal establishment and can be entitative or operational. Entitative attributes refer to God’s being. Some derive directly from His formal establishment (simplicity, perfection, infinity, immutability, and unity) and others mediately (goodness, immensity, omnipresence, and eternity). These make God transcendent, completely different from and above all created beings.
Operational attributes refer to God’s actions and can be immanent (internal): understanding and willing, and transitive (external): power. Understanding and will are vital operations, so divine life is also an operational attribute. God is endowed with will and is free. The effects of the divine will are love, joy, justice, mercy, and liberality.
God’s active power manifests in creation, maintenance, and governance (order).