Aristotle and Thomas Aquinas: Philosophy, Soul, and God

Philosophy of Aristotle

Aristotle was a disciple of Plato and the teacher of Alexander the Great. At the age of 18, he entered Plato's Academy, remaining there until Plato's death, after which he founded his own school, the Lyceum. His work relates to the philosophies of Parmenides and Heraclitus (providing a solution to their antinomies) and Plato (transcending Platonic dualism by valuing sensible being and rejecting the theory of Ideas, searching instead for the universal as the essence of things).

Metaphysics and the Four Causes

Aristotle conducted physical and metaphysical studies of being and its properties. Metaphysics is divided into ontology (the study of being as being) and theology (the study of the first cause of universal movement). He taught that all natural beings tend to reach their inherent perfection. Denying the independent existence of Plato's Ideas, he argued that perfection lies within the entity itself rather than in a separate realm of ideas.

In his physics, change is explained as the transition from potentiality to actuality (act and power). Material substances are composed of matter and form (hylomorphism), where matter is what something is made of, and form is its essence. For Aristotle, scientific knowledge is the knowledge of causes—the factors necessary to explain any process. He identified four causes:

• Material cause: That out of which something is made.
• Formal cause: The essence, pattern, or form of the thing.
• Efficient cause: The producer, agent, or source of the change.
• Final cause: The end, purpose, or goal of the thing.

In artificial things, there is also an exemplary cause (the model to follow). To explain universal motion, Aristotle posited the existence of an Unmoved Mover, a concept that demonstrates this movement and was later adopted by Thomas Aquinas.

Aristotelian Anthropology and Soul

In anthropology, Aristotle defined the soul as the vital principle of natural, living things. The body acts as matter, and the soul acts as form. The union of these two is natural and essential; consequently, there is no personal immortality of the soul. He classified three types of souls among living things:

• Vegetative soul: Found in plants, responsible for basic life functions like growth and nutrition.
• Sensitive soul: Found in animals, incorporating senses, movement, and appetite.
• Rational soul: Found in humans, enabling rational knowledge and free will.

The soul perceives through the internal senses (such as common sense, imagination, and memory). The appetitive faculty tends toward the good rather than evil.

Epistemology and Knowledge

In the field of epistemology, Aristotle asserted that human knowledge begins with sensible perception, from which the intellect abstracts to reach the universal, which is the true object of science.

Philosophy of Thomas Aquinas

Thomas Aquinas was born in the 13th century and died on his way to the Council of Lyon. He belonged to the Dominican Order and taught theology. He heavily adopted Aristotelian philosophy but integrated Christian elements into it. In politics, he agreed with Aristotle that man is by nature a social and political animal, but argued that supreme happiness is achieved only in the next world (heaven). He also integrated Aristotelian psychology and theology into a context dominated by Augustinian Platonic philosophy, which reflects the notions of exemplary cause and the world's participation in God.

Faith, Reason, and Theology

Thomas Aquinas made significant contributions to the relationship between faith and reason, as well as natural theology:

• Faith and Reason: Reacting against the development of the "double truth" theory, he denied it and asserted a clear distinction between faith and reason. Reason deals with the truths of the natural world, while faith deals with the articles of faith. He maintained that there are no contradictions between them because God is the author of both reason and faith.
• Theology and the Five Ways: Natural theology consists of truths about God that can be discovered through human reason. Aquinas proposed five ways to prove God's existence, distinguishing between two kinds of arguments:
  • He rejected a priori arguments (such as Anselm's ontological argument, which attempts to prove God's existence from His essence, because God's essence is unknown to us and not everyone conceives God as the greatest possible being).
  • He accepted a posteriori arguments, which start from facts of experience to demonstrate God's existence.