Thomistic Ontology: Structure of Reality and God’s Existence
In Christianity, there is a radical difference between God and other beings, creatures, which exist but may not exist. The contingency of created beings was noticed by Thomas Aquinas, who distinguished between essence and existence. Aquinas used this distinction as the basis for his system. This distinction is a fundamental principle in Thomistic ontology.
Aquinas states that the term “being” cannot be unambiguously applied to both God and creatures. God is Being, and creatures are beings in consequence of God’s free act of will. Being is said by analogy. The Neoplatonists affirmed that the first being is characterized by utter simplicity, while other beings are complex. In the Augustinian tradition, all realities except God are composite beings, consisting of matter, body and form, soul. Aquinas accepted the view of composition, but not the Augustinian formula.
The real and radical distinction between creatures and the creator is the essence and existence composition. This distinction fits perfectly with the contingent character of created beings, which exist but may not exist; their existence does not belong to their essence. Only in God are essence and existence identified; God cannot not exist. Thomas interprets this distinction through the concepts of potency and act, where essence is potency and existence is the act. Each core corresponds to a particular type of existence.
From the above, different levels of perfection are introduced depending on the grades of updated forms to essences. Thus, the degree of being of an intellectual being is more perfect than that of an animal. Essence essentially means the conjunction of characteristics that define what a thing is.
These beings also have a composition:
- Corporeal beings: matter and form, potency and act.
- Non-corporeal beings: immaterial, remaining “substantially” separate.
This distinction enables Aquinas to establish a hierarchy among different beings, taking into account their proximity to the creator:
- God at the cusp of the hierarchy
- Angels, intelligence areas, and separate human souls
- Human beings
- Animals
- Plants
- Inanimate objects
- The four simple elements
The structure of reality of created beings is an ordered whole, a cosmos, a system constituted of concentric spheres with perfect circular movement. In the center is the Earth, which is motionless; linear movement is not perfect. Aquinas explains the origin of the world by adopting the Christian conception, according to which God creates the world out of nothing. The world is as perfect as possible. If there are imperfections in the material, it is because of its nature. Aquinas states that it cannot be demonstrated that the world is eternal, but neither can it be proven that it was created in time.
Demonstration of God’s Existence
The existence of God is not evident to human reason, because not all people have the same idea of God. Thomas says that this idea comes from faith, and therefore, is an a priori argument and has no reason to be accepted by an unbeliever. Moreover, this argument contains an illegitimate step: going from the ideal to reality, thinking that something like existence that one wants to exist in reality: existence has no more reality intended to be thought than to be in our understanding, but not outside it.
For Aquinas, existence can only be established if we start from existence itself and argue in reliance upon it, and the only obvious and undeniable existence for us is the existence of the sensible. He develops five arguments, or “ways,” based on the evidence of sensitive experience, which is the first and most basic.