Louise asked:

Can you please explain Plato's use of the metaphor of shadows in the allegory of the cave in the
Republic? I am slightly confused.

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In order to answer your question it is important to clarify what exactly Plato intended to demonstrate
in his allegory of the cave. With an understanding of his intentions, it should be possible to
understand the role of the shadow metaphor.

Plato comments that in presenting his description of the cave he intends to, "..picture the
enlightenment or ignorance of our human condition..." One purpose of his description is thus to
demonstrate the differing ways in which humans understand the nature of reality. Specifically, Plato
wants to demonstrate that there is a fundamental difference between the everyday opinions of people
and true philosophical knowledge. Crucial to Plato's ideas is the distinction between non-philosophical
and philosophical understanding.

Layers of existence

Plato claimed that there are four "layers" of existence and that for each layer there is a corresponding
mode of knowing.By mode of knowing, I mean that in order to comprehend existence at each level,
certain tools and techniques of thought have to be utilized. These tools and techniques vary
according to the layer of existence they attempt to comprehend. I will refer to the layers of existence
as A, B, C and D. It would help if you were to visualise these placed in a vertical line with A at the top
and D at the bottom.

The layers are not equal in status. The layer of existence that contains imagesis considered to be the
most inferior. We can give this layer the label D. Images are completely dependent on material
objects for their existence and as such have a low status. The mode of knowledge that corresponds
to this layer (i.e. that mode of knowledge which contemplates images) is considered by Plato to have
a correspondingly low status.

The layer of existence that has a status above that of images is that layer which contains the world of
things.We can give this layer the label C. Plato is describing here the material world. It is the messy,
complicated and constantly changing world that we experience with our senses. The mode of
knowledge with which we comprehend this world has a higher status than that which comprehends
images but is still not the highest (and most true) way in which things can be known.

Plato makes a radical move and claims the existence of two other layers of existence (A and B),
neither of which is contained in the world of material things. Both these layers contain objects of
thought,and the modes of knowledge that apprehend them are purely mental (i.e. they have no
dependence on things in the material world). For layer B, the mode of thought that corresponds to it is
primarily mathematical reasoning, i.e. the use of inference and logic to create theorems from
fundamental axioms or starting points.

The highest and most perfect layer (A) contains what Plato describes as Ideals or Forms. These are
abstract concepts or ideas that, unlike the objects in the material world, do not change with time.
These ideas are, for Plato, the ultimate truths, untainted by exposure to the constantly changing
material world of layers C and D. Amongst many other things, this layer contains the perfect (and
true) idea of justice, along with the perfect (and true) idea/ design of a human being. Plato believes
that when we use a concept like justice in the material world (layers C and D), we are using an
imperfect copy of the perfect idea of justice that resides in layer A. When we identify an object as a
human being in the material world, we do so because it bears some resemblance to the perfect idea
of a human being that resides in layer A.

Layer A, more commonly known as the realm of the formsis contemplated by the highest mode of
knowledge. This highest form of knowledge is philosophy. The job of philosophers is to use their
minds to contemplate this realm and describe its contents accurately.

Plato believes that most people (non-philosophers) only ever use the modes of knowledge that
correspond to the two lower layers (C and D). In other words, most people have an understanding of
reality that is severely limited. What upset Plato was the fact that most people do not even realise that
there is another "higher" level of reality and that there is a correspondingly "higher" (more true) mode
of thought to accompany it. They spend their lives convinced that the type of knowledge they have is
the best, and are even prepared to defend this limited understanding in the face of challenges from
philosophy.

The Cave

In the cave, Plato describes the prisoners who, fastened so that they can only look at the back of the
cave, see shadows moving on the wall. Because these prisoners have spent their entire lives looking
at these shadows, they mistakenly assume that reality consists of these shadows. It is also perfectly
reasonable to assume that these people will have some form of knowledge that can explain and
possibly predict the movement of the shadows on the wall.

What the prisoners don't realise is that there is a world outside of the cave, a world of real objects,
and that the shadows represent these real objects in a very crude way. What they don't realise is that
if they were to free themselves from the cave and go into the world outside, their mode of knowledge
which comprehended the world of shadows would be utterly unsuitable as a guide. Any ideas they
held about the nature of the shadows would seem completely inadequate and trivial when it came to
dealing with the source of the shadows. Some of the prisoners may even deny the existence of a
world outside the cave and challenge anyone who claimed otherwise.

Hopefully it should be clearer now what the shadows in the cave represent. They represent the reality
experienced at levels C and D of reality. The knowledge that the prisoners create in order to
understand the movements of the shadows represents the limited mode of knowledge utilized (and
cherished) by those who do not accept the existence of a higher layer of reality. And just as the
prisoners mistake the world of the shadows as the truest form of reality, so do the non-philosophers
when they deny the existence of any layers of reality above C and D.

The world outside of the cave, where the real objects that create the shadows exist, represents layer
A. And just as the prisoners, upon leaving the cave, will be forced to abandon their old ways of
understanding their world, so will the person who realizes the existence of layers A and B. They will
be forced to think philosophically.

Simon Drew