Thomistic Philosophy: God, Reason, and Being
Existence of God
The Problem of Demonstration
We might think that God can be directly perceptible by reason, the way we see truths like “triangles have three sides.” St. Thomas calls these propositions self-evident. In them, the predicate is included in the subject because the essence of its object is the property referred to in the proposition. They are also evident to us when we see them as real with just understanding the concept’s subject. If the existence of God is included in its essence, then we could grasp the truth of the proposition “God exists” with the mere understanding of the term “God.” Some philosophers (e.g., St. Anselm) believe that you can demonstrate the existence of God on this assumption (the “ontological argument”). St. Thomas, however, maintains this cannot be an argument of this kind because the essence of God is not given to us as clearly as, say, the essence of a triangle. This means that the proposition “God exists” is not obvious to us, even if self-evident (it is true that existence is included in the essence of God).
The Five Ways
According to St. Thomas, rational demonstration of God’s existence alone is not adequate because it is not according to human faculties. We must derive knowledge of God from sensible experience. His evidence (the Five Ways) has antecedents in Plato and Aristotle and are a posteriori demonstrations from the effects of God’s action in the world to trace back to Him as the ultimate cause. The five ways are: via motion, the efficient cause, contingent being, the supreme being, and the governance of the world.
Connecting Faith and Reason
For Aquinas, the philosophy/theology distinction rests on the separation between the natural order and the supernatural order. The natural order of knowledge comes from human reason, results in philosophy, and is demonstrable. The supernatural order proceeds from revelation and faith, and this knowledge is obscure. Some of its truths are available to reason, and others exceed it. Both kinds of knowledge come ultimately from God, so between them, there can be no contradiction. Collaboration between the two areas of expertise results in theology: revelation can guide reason and help it avoid errors, and reason serves faith to clarify and defend the mysteries of revelation. Some beliefs can never be proved by reason, while others can, such as the preambles of faith (God’s existence and the immortality of the soul).
There are two types of theology:
- Rational or natural theology: Reaches God using a capacity linked to human nature: reason.
- Christian or supernatural theology: Its foundation is revealed doctrine and faith, but it also uses reason to achieve scientific understanding and as a dialectical weapon.
Politics
The human being is by nature a social animal, but at the same time has a transcendent end. This is reflected in social organization, which revolves around the supernatural and earthly power. State and Church are independent and autonomous institutions, but the state must seek the common good, which is identified with natural law. Aquinas thinks political and religious power are autonomous and compatible, but ultimately, temporal power is subordinate to religion.
Metaphysics
Essence and Existence
For Aquinas, essence is what defines an entity. It is composed of matter and form. Both components are created and contingent. It’s what all people share of the same species and is identified with the Aristotelian potentiality: it is what can potentially exist. Existence is that by which the essence exists. It is identified with the Aristotelian act: that which actualizes the essence.
The Problem of Individuation
Matter does not belong to the category of quantity and, therefore, cannot be measured or calculated. Individuality occurs when matter is provided with measurable and calculable dimensions when the accident of quantity is incorporated into the matter. The principle of individuation is, therefore, matter under the category of quantity.
Contingent Being
The Third Way explains that the universe is contingent. This contingency requires a necessary being that created the universe, a necessary being to actualize essences and bring them into existence: God. God is pure act and cannot be identified with potentiality, as stated in Exodus (“I am who I am”). While created realities are composite (and thus have an essence), God’s essence is to exist. Therefore, God’s existence is necessary, and creation is contingent. The distinction between essence and existence serves to show, first, the contrast between divine necessity and the contingency of creation and, on the other hand, the need for God’s existence for the world to exist. This distinction also emphasizes the idea that the universe is created and not eternal, distancing Aquinas from the Averroists.
Anthropology
Aquinas applies the Aristotelian hylomorphic theory to humanity, according to which man is a composite of matter (body) and form (soul). This union is not accidental, as in Augustinian Platonism, but substantial. However, in agreement with Plato and, above all, Christian thought, the soul is incorruptible, immortal, and subsistent; it does not need the body to exist and was created directly by God.
Knowledge
Knowledge always starts with sense data. Aquinas’s empiricism led him to reject the existence of innate ideas in the mind. The mind is a tabula rasa, and all ideas are formed from what has been captured by the senses. There are some exceptions, such as the authors of the scriptures, whose knowledge comes from divine illumination.
There are two types of knowledge:
- Sensitive knowledge: The human being captures reality through the senses. The beginning of all knowledge is sensitive. Subsequently, through imagination, an image of reality is formed in the mind, which Aquinas calls a “phantasm.”
- Abstract knowledge: The intellect performs two operations: abstraction, by which the common aspects are taken from a diversity of objects, and the formation of universal concepts from the information obtained by the intellect. This process is performed by the passive intellect.
The Five Ways provide an indirect knowledge of God.
Ethics
Aquinas assumes a hedonistic ethic and recognizes that all natural beings tend toward an end. In man, this end is happiness. He identifies happiness with virtue and distinguishes two kinds of virtues: theoretical and ethical.
- Theoretical virtue: Develops the theoretical virtues and aims to achieve happiness through contemplative beatification. An example: the saints. True happiness is only in heaven, attainable through God’s grace.
- Ethical virtue: Develops moral virtues and aims to know God and choose good things through reason. Natural law is written, universal, and unchanging, universally acknowledged, although sometimes breached. These are laws born from God.
Aquinas defends the existence of natural laws, distinct from positive laws (written rules for organizing society), which should be inspired by natural law.