Plato and Aristotle: Contrasting Metaphysics and Epistemology
Plato vs. Aristotle: Ontological Dualism
For Plato, true reality resides in the World of Ideas. For him, the physical world is merely an imitation of these truly real ideas. The World of Ideas comprises concepts that are immutable, eternal, intelligible, and universal (inspired by Parmenides’ characteristics of Being). This world is apprehended through reason; the rational soul comes to know these values.
The physical world consists of sensible things perceived through the senses. These are finite, mutable, unintelligible, and individual (inspired by Heraclitus’ characteristics of Being). This world is known through the body, and what is apprehended is the material world.
For Aristotle, only the sensible world constitutes authentic reality. This world is composed of concrete, sensible beings. He affirms the multiplicity of beings as the sole reality, distinguishing between primary substance (the particular), which is unlimited and unknowable in itself, and secondary substance or essence (the universal). This distinction arises from the concepts of matter and form, where form is the natural essence of a being, and forms are intrinsic to the being itself.
Aristotle explains that movement or change exists, utilizing two concepts: potency and act.
- A being in potency possesses the ability to realize its own being; it is that which is not yet but can become.
- A being in act is that which already is.
Thus, movement is defined as the transition from potency to act, encompassing two types of change:
- Substantial change (generation and corruption)
- Accidental change (alteration in place, quantity, or quality)
To further support the concept of movement, Aristotle relies on the theory of four causes. According to this theory, there is always an efficient cause that initiates movement and a final cause (or telos) that it serves. This culminates in the concept of the First Unmoved Mover and the idea of perfection as the ultimate end.
Plato vs. Aristotle: Theories of Knowledge
Aristotle’s Epistemology
Aristotle’s theory of knowledge posits that understanding the sensible world begins with the perception of sensory data, but these are not understood as Platonic ideas. He moves through phases to grasp the form and secondary substance through intellectual concepts, employing an inductive method that progresses from particular observations to universal understanding. This process involves several stages:
- Sense Perception: The senses receive specific individual sensory data. Common sense then integrates these perceptions to form an initial impression of the being.
- Imagination: The ability to recall or form an image of a concrete being even when it is absent.
- Memory: Compares and retains these imaginative images, forming a collection of ‘phantasms’ or mental images.
- Intellect/Understanding: Abstracting from the particular phantasm, the intellect grasps the universal essence or form, thereby forming concepts and linking them to make judgments.
Plato’s Epistemology
For Plato, true knowledge must be knowledge of ultimate reality. This true knowledge, residing in the World of Ideas, is attained through contemplation by the rational soul, progressing through dialectical phases:
- Eikasia (Imagination): Confusing an image or reflection with the sensible object itself.
- Pistis (Belief): Distinguishing sensible things from their images, but still relying on sensory experience.
- Dianoia (Discursive Reason): Understanding mathematical and scientific concepts, acknowledging the existence of Ideas, and preparing the rational soul for contemplation.
- Noesis (Intellectual Intuition): The rational soul directly apprehends the Forms or Ideas, achieving true knowledge.
Since the sensible world is not true reality, knowledge derived from it through the senses is not genuine knowledge but merely doxa (opinion).
Key Differences in Epistemology
Aristotle rejects Plato’s theory of reminiscence. He argues that the process of knowledge is an inductive process of abstraction, moving systematically from one stage to the next. He contends against Plato that there is no unbridgeable qualitative leap between doxa (opinion) and episteme (true knowledge), and that one can indeed move from sensory experience to genuine understanding without accepting a separate realm of Ideas as authentic reality.