Aristotelian Realism: Being, Knowledge, and the Universe

Aristotelian realism is based on resolving the problem of being and knowledge. Aristotle provides a triple response to the static monism of Parmenides, the mobile philosophy of Heraclitus, and the idealism of Plato.

Aristotle’s Response to Parmenides’ Monism

Aristotle breaks from the unitary, compact, static, motionless, and undifferentiated being introduced by Parmenides. He introduces the concepts of “being per se” and “being per accidens,” as well as the notions of act and potency. Aristotle affirms the pluralism of being: not a single being, but many beings. The universe consists of individuals, and nothing prevents the existence of many beings. Applying the theory of act and potency allows him to account for the movement of beings. All beings are mobile except God, but they move in different ways. Celestial substances move only in circular motions, while terrestrial substances move locally and undergo generation and corruption.

Aristotle’s Response to Heraclitus’ Philosophy of Change

Against Heraclitus, Aristotle supports the concept of movement but simultaneously affirms the permanence of essence. Particular beings move, but essences are timeless and remain through all changes and mutations.

Aristotle’s Response to Plato’s Idealism

Against Plato’s idealistic pluralism, Aristotle argues that there are not two ontologically different worlds, but one. Latter substances have no ontological reality but a logical one. True ontological reality belongs to primary substances, which come in three varieties: terrestrial, celestial, and divine.

Four Perspectives on Aristotelian Realism

  1. From the perspective of act and potency: Beings start as pure matter, a physical potential, and move up in a chain of increasingly perfect events until reaching pure act, unadulterated by potency, which is the summit of being.
  2. From the perspective of matter and form: Initially, there is a field without any form. Through a series of beings whose forms are becoming more perfect, we reach a pure form without matter, which is God.
  3. From the perspective of motion: The universe is composed of many mobile beings concatenated with each other, culminating in a Prime Unmoved Mover. This mover is not moved by another but moves itself and causes all other movements; it is God.
  4. From the perspective of the end: Everything tends toward its own perfection, its particular purpose. Potencies tend toward acts, and the universe tends toward God, the ultimate cause of all being and movement.

Hierarchical Levels of the Universe

The universe, according to Aristotle, is structured hierarchically into three levels:

  • The physical terrestrial world: This includes raw materials and the four elements. It is mobile, composed of matter and form, potency and act, and subject to movement, mutation, generation, and corruption. Material elements are eternal, while individual beings are contingent and perishable. This level encompasses non-living things, including principles (matter and form), elements (earth, water, air, and fire), and mixtures (indefinite number).
  • The celestial physical world: This level includes spheres and stars, which are moving substances, eternal, ungenerable, incorruptible, and equipped with intelligent and highly perfect life forms. They are graded into 84 spheres that revolve around the Earth in a perfect circular motion. At its end is the last sphere, informed by the supercelestial Unmoved Prime Mover.
  • Divine substance: This is an eternal, simple, immovable, incorruptible substance, a pure form without any mixture of material, a pure act without potency. This substance is God. God did not create the world, which is eternal, nor did He take part in its organization. His only intervention in the world is to cause movement through attraction and love.