Prisoners of Solipsism and Prisoners of the Cave
In meditation II of his Meditations on First
Philosophy, Descartes writes that the only things he knows with certainty
is “I am," "I think” and “I am a thinking thing”.
At this point in
his meditations Descartes reports that he does not know anything else
that is certain, including his lifelong belief that there are things “external”
to him, for example, physical objects, human bodies, other thinking things, and
God. Descartes finds himself quite alone.
But not alone in the universe because for all he knows, he is the
universe. He does not know if there is a
universe that exists apart from the content of his own mind.
Descartes knows with certainty that he exists as
a thinking thing, that is, a thing that has thoughts, doubts, affirms, denies,
and has a multitude of visual, auditory, olfactory and tactile sensations,
including the feelings of pain and pleasure.
What he does not know is whether there are any other thinking beings. He might see or hear what appears to be
another human being, but he does not know with any certainty whether he is
dreaming or hallucinating the thing that he senses.
This is a theory now known a solipsism, or
as some would call it, “all-alone-ism.” It is the theory that although I can
know with certainty that I exist, I cannot know with certainty that there are any other thinking beings, nor for that matter, any non-thinking beings. For example, I now have a mental image of a rose bush. But this is not sufficient to allow me to draw
the certain conclusion that there is an actual rose bush, existing external to my
mind, that is causing me to have this mental image. For all that I know, the rose bush I claim to
sense might not exist at all. I might be hallucinating
or dreaming about a rose bush.
In meditation VI, Descartes summarizes the
reasons why he cannot confirm that physical objects are the cause of the images of physical objects that are in his mind.
His senses give him confusing information about the size and shape of
objects. He cannot distinguish between
the ideas he allegedly gets through his senses and the ideas that he has when
he is dreaming. And although he cannot
control the images that appear to come into his mind from his senses, this is not sufficient
to confirm the existence of an external world because these images could just a
well have been caused by some unknown faculty within himself.
Descartes’ solution to these problems is to invoke
both the existence and participation of God.
In meditations III and V, Descartes believes he has proved the existence
of a supremely perfect God. He asserts
that God has created human beings who “naturally” assume that the mental images
or ideas that they have of material objects are caused by real material objects
in an external world. The dubious natural “habit” of believing that what we
learn from the senses is true is a gift of nature, and “nature, … is nothing
more than God himself.” Since God is all-good, he would not deceive us about
our natural belief that there is a world external to our mind, populated by physical
objects and human beings like us. Although
Descartes admits that the ideas (images) of objects that we receive from or through
the senses do not always perfectly resemble the material objects that causes
these ideas, he believes that he has made a convincing argument for the claim
that solipsism is false. We live in a
world of material objects and other human beings. We are not alone.
This leaves the reader with two questions. If there is no convincing argument for the
existence of a supremely perfect deity and/or that God would not allow us to be
deceived by our senses, are there alternative ways to avoid solipsism? To be specific, based only on Cartesian
assumptions about the large conceptual gap between the internal world of mental
ideas (images) and an external world of other minds and material objects, is
there a way to bridge the gap that does not involve the deity?
Plato might be of some help here. In Republic, Book VII, Plato has the
character Socrates entertain his friend Glaucon with one of the most famous
thought experiments in the history of philosophy: The Allegory of the Cave.
In the allegory, the character Socrates asks Glaucon to imagine prisoners “living in an underground, cave-like dwelling, with an entrance a long way up, which is both open to the light and as wide as the cave itself. They’ve been there since childhood, fixed in the same place, with their necks and legs fettered, able to see only in front of them, because their bonds prevent them from turning their heads around” (Republic, VII, 514). They stare at a cave wall on which images are projected. These images are cast from carved figures (puppets) illuminated by a fire and carried by people on a parapet above and behind the prisoners. They see nothing of themselves and one another. They only see “the shadows that the fire casts on the wall in front of them.” If one of the prisoners is released from his chains “and suddenly compelled to stand up, turn his head, walk, and look up toward the light, he would first see the puppets and the fire" (id., 515).
There is more to the allegory, and there are many
interpretations of it. I will not enter
this debate. I want only to indicate
that in the allegory, the prisoners discover and can verify that the images
they see on the wall are in fact shadows caused by puppets that are paraded in
front of a fire. The prisoners see all
at once the images, the fire and the puppets, thereby confirming the causal
connection between them.
Compare this to Descartes’ “prisoners of
solipsism.” They are thinking beings who
live in the internal world of their own minds and yet have a “natural” habit of
believing that there is an external world of material objects from which their
ideas of material objects proceed. But
these prisoners have no way to confirm this causal connection. Unlike the cave
prisoners who upon release, see puppets casting shadows on the cave wall,
Descartes’ thinking beings cannot put themselves in another location from
which they can “see” images being projected into their mind by material
objects that exist outside their mind. Plato’s prisoners can turn around and
see the puppets being manipulated in such a way that they cast shadows on the
wall. But Descartes’ prisoners are
trapped in their own mind. They cannot
break out of their mind, go out into the external world and watch corporeal
objects cause their mind to be populated with new images.
If Descartes’
hypothesis of a causal connection between the external world and the mind
cannot be verified or falsified, then
surely an agnostic solution of the solipsism problem collapses. If there is no God to assure the prisoners
that their senses can be trusted, then they will never know whether there is an
external world and other minds. They can
theorize about an external world but there is no way they can either confirm or
falsify these theories.
This brings us to a second question. Is the problem of solipsism a problem of Descartes’
own making, based on false assumptions, or is it a genuine problem, worthy of
our attention? If it is a
pseudo-problem, then Descartes (and those philosophers who he inspired) need to
be liberated from their false assumptions.
As the twentieth century philosopher Ludwig Wittgenstein famously put
it, the job of philosophy is “to show the fly the way out of the fly
bottle.” Is Descartes a fly trapped by
his own unsupported assumptions?
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For more commentary and critique on Descartes, see Laurence Houlgate's new book Understanding Descartes: The Smart Student's Guides to Meditations on First Philosophy, available through his website: www.HoulgateBooks.com Also: once on the website, go to the tab that has a short video in which the allegory of the cave is enacted by clay puppets.
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