Plato’s Divided Line: Reality, Knowledge, and Philosophy
Plato’s Divided Line: Understanding Reality and Knowledge
Plato’s Divided Line clearly illustrates the dualism of Platonic philosophy regarding the conception of reality and knowledge. Plato establishes a clear correspondence between the structure of reality and forms of knowledge because, as he stated, the quality of knowledge depends on the nature of the objects known.
Plato illustrates this relationship between reality and knowledge with a line first divided into two main parts:
- The sensible world, to which corresponds apparent knowledge or mere opinion (doxa).
- The intelligible world, to which corresponds real knowledge or true knowledge (episteme).
Each of these two main parts is then divided, in turn, into two further segments, so that the line is ultimately divided into four parts. Plato assigns to each part a specific type or class of being:
- Two belonging to the sensible world: images and natural and artificial bodies.
- Two from the intelligible world: mathematical entities and Ideas (Forms).
Correspondingly, Plato assigns one of these four kinds of knowledge to each of these four types of beings:
- Conjecture (eikasía)
- Belief (pistis)
- Inferred truth (dianoia)
- Intuited truth (noesis)
These levels of knowledge also correspond to the four faculties we use to apprehend each of the four types of beings:
- Imagination for understanding images.
- Senses for understanding natural and artificial bodies.
- Discursive reason for understanding mathematical entities.
- Intellectual intuition for the knowledge of the Ideas.
Branches of Knowledge on the Divided Line
The body of knowledge concerning the entities of the sensible world is physics, which for Plato is not considered true science because its knowledge is neither universal nor necessary; it consists of mere opinions.
The body of knowledge of mathematical entities is mathematics, which is considered a science because its principles are universal and necessary.
The body of knowledge about the Ideas is dialectic, considered by Plato the supreme science, as it pertains to the eternal and immutable beings of the intelligible world.
Plato’s Divided Line: Degrees of Knowledge Explained
Eikasía (Conjecture)
This is the knowledge of images, shadows, and reflections of sensible things, which the imagination weaves into all sorts of fantasies (e.g., mythological beings). The objects of this knowledge are not directly visible, demonstrable, or intuited.
Pistis (Belief)
This is the knowledge of natural and artificial entities directly perceptible to the senses. These objects are not provable or intuited; it is a matter of belief.
Diánoia (Inferred Truth)
This is the knowledge of mathematical entities whose existence is inferred rationally. These mathematical entities are intermediate realities between the intelligible and the sensible world because, like the Ideas, they are eternal, and like sensible things, there are many instances for each species (e.g., the triangle, rectangle, sphere, etc.). As part of both the sensible and intelligible worlds, Plato considers mathematical knowledge as a prerequisite or propaedeutic step to access true knowledge, the knowledge of the Ideas.
Noesis (Intuited Truth)
This is the knowledge of Ideas. They are known directly without the aid of the senses, through pure intellectual intuition. This intuition is carried out through what might be called ‘the vision of the soul’ (nous). The science that corresponds to this degree of knowledge is dialectic.