Aristotle's Metaphysics: Unmoved Mover and Four Causes

The Unmoved Mover and Pure Act

For Aristotle, if something is moving, it is because the movement was previously in potentiality, and it was another substance that communicated it into actuality. The chain of things that move and are moved cannot be infinite. Therefore, the existence of a first mover is necessary—one that moves without being moved itself: the Unmoved Mover.

The Concept of Potentiality and Actuality

This concept is reached by considering the Mover as a pure form, already realized as Actus Purus (Pure Act). The substrate is the realm of possibility. Aristotle called this conceptual substrate First Matter, which is pure potentiality, pure plasticity without specific form or concretion.

If we place First Matter at one end of the explanatory scale, and hylomorphic compounds (which are bodies) in the middle, the upper limit is occupied by pure perfection—that which is immaterial. This concept, the Pure Act, appears as a transcendent reality to our world. We arrive at the climax of the Aristotelian system: absolute perfection, God. Without undergoing any transformation, God acts as the Final Cause, moving the entire universe.

Aristotle, who had begun his search trying to explain nature by itself, without reference to anything external or superior, ultimately accepted the existence of a reality that guides the world and gives it meaning. In the end, this conclusion was similar to what Plato had advocated.

Aristotle's Theory of Causality

Aristotle used the expression translated by the word "cause" to refer to four factors that provide a full explanation of a phenomenon, although only one of these factors corresponds to the sense in which we typically use the term today. We can speak of four factors:

• The Material Cause: The substrate of change.
• The Formal Cause: The definition or essence acquired with the change.
• The Efficient Cause: The agent or source of the change.
• The Final Cause: The purpose or end goal of the change.

These four factors must be known if we are to have a complete explanation of a fact.

Teleology and Natural Place

Matter, form, and efficiency are essential, but the ultimate reason for existence is the purpose of the act. It is the Final Cause which sets in motion all the springs of life and gives meaning to their dynamism. Nature does nothing in vain; everything responds to a purpose and objective. This corresponds to the so-called finalist or teleological vision.

The area that most easily demonstrates the Final Cause is surely biology. But even in the domains of physics, Aristotle observed the tendency of elements to be fully realized. In Aristotelian physics, everything has its own place—the natural place—which is where it belongs. This theory of natural places necessarily leads to the defense of geocentrism.

Synthesis of Predecessor Philosophies

Aristotle provides a synthesis of all previous thought:

• The Ionians focused on the Material Causes of things.
• The Pythagoreans and Plato focused on the Formal Cause.
• Empedocles and Anaxagoras introduced the idea of the Efficient Agent.

Aristotle's merit was discovering the limitations of each of these partial explanations of reality and integrating them all into one comprehensive and coherent framework.