Thomas Aquinas on God's Existence and the Human Soul

The Third Way: Argument from Contingency

The Third Way posits that man is a contingent being; that is, he is not necessary. The world existed without us, and it will exist after us. Some things can exist and not exist, since they are produced and destroyed. If everything were contingent, there would have been a time when nothing existed. However, nothing can come into being if not by virtue of something that already exists. Therefore, there must exist a necessary being that brings others into existence, which is God himself.

The Fourth Way: Degrees of Perfection

The Fourth Way believes that there are degrees of perfection in human beings. We speak of degrees because we have an idea of perfection; for example, we say a person is more or less wise. We could not say this unless we thought there was a supreme being with whom we could compare them, and that being can only be God.

• We see that there are things better and worse.
• The 'more' and 'less' attached to things function as they approach a maximum.
• We could not compare things unless there was something that acts as a maximum.
• This being, with which all things are compared, is God, the supreme being.

The Fifth Way: Argument from Finality

Everything has an end; all things serve a purpose and have a finality. This is fulfilled because only an intelligent being can ensure compliance with a goal. We see that things, even those lacking knowledge, act toward ends. Since something without knowledge cannot tend toward an end unless directed by an understanding being—much like an archer guides an arrow toward a target—there must be an intelligent being that directs all natural things to an end. This being we call God.

Thomistic Anthropology: Body and Soul

For Saint Thomas, God created man as a unique substance composed of body and soul. The soul is the act of the body and the radical principle of life. The rational soul of every man is immortal and exists by itself without the need of the body. In contrast, the souls of animals depend on the body for all operations and are not immortal. For Saint Thomas, the body belongs to the essence of man; upon death, the body corrupts, but the soul remains alive.

The Three Parts of the Soul

• Vegetative: Present in plants, animals, and man; it provides life, reproductive capacity, and growth.
• Sensitive: Present in irrational animals and man; it includes the five external and internal senses.
• Rational: The unique understanding of man that captures and knows the essence of things.

The Thomistic Theory of Knowledge

The process of knowledge follows a specific ordering:

1. The Senses: These grasp the sensitive object particularly, such as a man, a tree, or a house.
2. The Imagination: This is where the phantasms (images of objects) are recorded.
3. The Intellect: It takes those images of fantasy and performs an abstract function, extracting only the essentials.
4. Understanding: This information goes to the understanding, which develops the universal concept by applying the agent's data to the specific object.