Epistemology comes from two Greek words- episteme (knowledge) and logos (reason, word, study), which taken together means study of knowledge. Within philosophy, epistemology is the process of understanding “How one knows something” or “What is happening in our minds” when the person knows something. In this essay, I will compare the epistemologies of Plato and Aristotle.
To understand Plato’s epistemology, one first must understand his psychology of the human person. Psychology, the study of the mental states or processes, of the person for Plato is a tri-part division of reason, passion and appetite. His psychology states all of these parts are necessary but not equal in value. Reason, represented by the philosopher-king, is the highest in value because reason has access to both the sensible and intelligible realms of knowledge. Reason within the intelligible realm knows the Forms. A characteristic of these Forms is that Ideas (eidos) have a feature that is expressed in a fully infinite, non-partial way. There is also a Form of the Form which is in the Good.
Plato uses three analogies to demonstrate his epistemology. The first is the analogy of the Sun. The light from the Sun shines on objects so that one can see them. In like manner, The Form of the Good, illumines the other forms such as the Form of Truth, the Form of Beauty or the Form of Justice, so that one can understand them. The second analogy of The Line, shows the progression of knowing. Knowledge begins at the shadows (eikas) stage, progresses to the actual object (pistis) stage, then to broader study of a number of objects (diania) to finally one arrives at the essence or Form of the object (noesis). The third analogy, The Cave, shows how most men see knowledge which is a distorted dim reflection cast on a wall. One usually will need to be dragged out of this situation into the realm of Light, illumined by the Sun, which is a metaphor for the Form of the Good.
Plato’s anthropology must be considered as well. He believes that soul is the true essential part of man. “I am” my soul which is currently trapped in this body. The term for this view is dualism. The analogy of a pilot on a ship is useful in understanding Plato’s perspective. This understanding of the soul, leads him to believe that the soul can know in the Forms innately.
From considering Plato’s psychology, his analogies, and his anthropology his epistemology is one of man having innate ideas impressed on his mind from the Forms and that senses are useful only triggering recollection of these ideas. Knowledge is found in turning away from the senses. It is an interior way of knowing.
Aristotle’s psychology of the soul is different. Instead of a tri-part understanding, he divides the soul into two parts with each of these parts having two branches. The two main parts of the soul are the rational and irrational parts. The rational part of the soul branches into reason and appetite, while the irrational part divides into the appetite and vegetative-nutrition-growth. The soul then manifests itself in four ways- Reason, Motion, Sensation, and Nutrition/Growth.
The rational part having a role in the middle appetite section gives rise to his hylomorphic anthropological view of man. Unlike Plato’s dualism, Aristotle considers the person to be an embodied soul. Because of this bodied expression, the person comes to know things through the senses. His process of knowing is three-fold: 1. Sense perception, all lower animals have this, 2. Retained memory, experience, and 3. Recognition, nous, or wisdom. Aristotle does not believe in innate knowledge only innate potentials (capabilities) to know. Knowledge is found from the senses. It is an exterior way of knowing.
In conclusion, the differences in Plato and Aristotle’s epistemologies are as follows. Plato’s Soul has three parts versus Aristotle’s soul of four parts. Plato is a dualist whereas Aristotle is a hylomorphoricist. Plato’s soul is evidenced in only thinking while Aristotle sees the soul in thinking plus the bodily sensible operations of motion, sensation, and growth. Plato sees wisdom coming from within, with the senses used to recollect innately the ideas of the Forms. Aristotle sees the senses exteriorly providing the knowledge that the soul has. For him, there is no innate knowledge.