Prior to Socrates and Plato (in the Presocratic tradition), there were two conceptions of reality:
(represented by Parmenides) and the other essentially
by Heraclitus). According to the first, reality is one and unchanging. According to the second,
reality is changing.
Plato's conception of reality distinguishes between the changing world of appearances (the
sphere of the spatio-temporal world) and the world of unchanging and eternal reality. The world
of appearances is the VISIBLE WORLD of particular things, and it is characterized by
mutability (i.e., change). The real world is suprasensible (beyond our senses) and the
INTELLIGIBLE world. Plato combines the Heraclitean doctrine of flux and the Parmenidean
principle of reality as unchanging to show that there is a distinction between two realms: an
intelligible one grasped by the mind (by intuition and reflection) and a sensory one grasped
through the senses. The former is unchanging and immaterial; the latter mutable and material.
B. Doctrine of the Forms (
According to Plato, the real world is constituted by abstract entities called
First, in the VISIBLE WORLD we find a plurality of substances under the same name (e.g.,
table, chair, tree, guitar). Each of these substances has a corresponding "nature" or "quality"
which is represented in particular instances. Every substance has an essence (its essential
properties). According to Plato, what we grasp under a concept of a thing (i.e., its essence) is not
merely a subjective concept (an idea in our heads), but an objective essence, something which
has existence independent of any particular instance. Such an entity is a Form. And there would
appear to be as many Forms as there are natural objects that involve an instantiation of a
universal concept. Furthermore, in the VISIBLE WORLD, we make judgements that involve
moral and aesthetic universals (so-called abstract ideas), x is good, x is just, x is beautiful. Like
natural objects (who essence exists independently of any instantiation in the physical world), so-
called properties (like goodness, justice, and beauty) also exist independently of their
instantiations in substances.
actual horse => real horse
"x is just" = > real justice
Unlike the instantiation of an essence in a particular substance, a FORM is perfect
INDEPENDENT OF SENSIBLE PARTICULARS
FORMS belong to the INTELLIGIBLE REALM of BEING.
They are imperfectly represented in the VISIBLE WORLD of BECOMING.