Aristotle’s Philosophy: Act, Potency, Physics, and Cosmology
Filo 2.2 & 4. Potency and Act
The distinction between potency and act addresses the physical explanation of movement. While Parmenides saw reality as static and Heraclitus viewed it as constant evolution, Plato proposed two worlds: the Sensible (changeable) and the Intelligible (immutable ideas). Aristotle, however, introduced Being (act) and a form of non-being: potency. He believed this explained change in substance, with two aspects: “what is” (act, e.g., a tree) and “what it can become” (potency, e.g., a seed). Aristotle saw movement as a progression from potency to act. Unlike Parmenides’ static Being, being-in-act comes from being-in-potency.
Motion or change types include:
- Substantial changes: generation (becoming) and corruption (ceasing to be)
- Accidental changes: quantitative (increase, decrease), qualitative (alteration), and locative (movement)
Act has priority over potency; a seed comes from an existing tree. Aristotle held a finalist or teleological view of reality. Potency-act and matter-form are parallel: matter is like potency, form actualizes matter. Act is always the way.
V. Aristotelian Physics
Physics was central to Ionian philosophers like Empedocles, Anaxagoras, and atomists. Parmenides distrusted sensory knowledge, and Plato saw nature as conjecture. Aristotle valued nature as a source of scientific knowledge, seeing beings as composites of matter and form in motion. Nature is as valuable a knowledge source as mathematics or theology.
1. Nature (physis)
Physics’ purpose is understanding physis or nature, the principle or cause of substantial movement in natural beings. Nature is the way of being, an inherent principle of development and transformation. Aristotelian substance is a developing being, especially in living organisms, reflecting Aristotle’s biological focus.
2. The Four Causes
Scientific knowledge requires understanding causes. Physics establishes causes of natural things. Aristotle defined causes as factors explaining processes, criticizing predecessors for focusing on single causes. He proposed four causes:
- Material cause (what something is made of, e.g., wood for a table)
- Formal cause (the form or essence, e.g., the table’s design)
- Efficient or driving cause (the agent of change, e.g., the carpenter)
- Final cause (the purpose or end, e.g., support)
The material cause is the substrate. The formal cause is the essence. Formal and material causes are intrinsic. The efficient cause initiates change, and the final cause gives it meaning. Efficient and final causes are extrinsic in man-made objects but intrinsic in living beings, where formal, efficient, and final causes coincide (e.g., a man begetting a man).
4. Cosmology
Aristotle distinguished two cosmic regions:
- The Supra-lunar World: Stars are eternal, incorruptible beings made of ether, with perfect circular motion. They are moved by spheres and a prime mover. The universe is finite, with no vacuum, and Earth-centered.
- The Sub-lunar World: Characterized by generation and corruption, with linear motion (up or down) due to the nature of elements (fire/air up, earth/water down). Aristotle posited a first mover as the cause of eternal motion, acting as both an efficient cause (through contact) and a final cause (as an object of desire), a purely immaterial, living, happy, and self-sufficient entity (God).
VI. Anthropology
Body and soul form a single substance, like matter and form. Aristotle rejected reincarnation; the soul fits its body like the eye’s sight. Body and soul are inseparable; a bodiless soul is nothing. He denied the soul’s preexistence or existence after death. Unlike Plato’s tripartite soul, Aristotle emphasized the soul’s unity throughout the body. Knowledge involves the whole person, body and soul, combining sense knowledge and intellectual knowledge.
The soul has functions:
- Nutritive or vegetative (growth, nutrition, reproduction)
- Sensory (perception, desire, movement)
- Thinking (intellect and understanding)
Plants have only the first, animals the first two, and humans all three. Knowledge is a whole-person experience.