THE SEARCH FOR INDUBITABLE TRUTH
This made the first and most important problem the search for a
single indubitable truth. Where can we find such a truth? Most
of the knowledge about existing things that we normally deal with
does not require indubitability, in most cases good
approximations to the truth are sufficient. We can easily set
these things aside. Senses have always been considered suspect.
Different people perceive the same things differently and the
same person can perceive the same thing differently at varying
times and under differing conditions. So we can set aside those
ideas which we gather directly from our senses. This,
essentially, was Descartes' route to indubitability. Through
systematic doubt he set aside any idea that was thought to be
true but that was not clear and distinct, meaning that its
rejection did not lead to any contradictions.
But this was not sufficient for the kind of absolute necessity
that. Descartes was searching for.
He took one more step beyond that, as we can see from this
excerpt from his first meditation.
I shall then suppose, not that God who is supremely good and
the fountain of truth, but some evil genius not less
powerful than deceitful, has employed his whole energies in
deceiving me; I shall consider that the heavens, the earth,
colors, figures, sound, and all other external things are
naught but the illusions and dreams of which this genius has
availed himself in order to lay traps for my credulity; I
shall consider myself as having no hands, no eyes, no flesh,
no blood, nor any senses, yet falsely believing myself to
possess all these things; I shall remain obstinately
attached to this idea, and if by this means it is not in my
power to arrive at the knowledge of any truth, I may at
least do what is in my power [i.e. suspend judgment], and
with firm purpose avoid giving credence to any false thing,
or being imposed on by this arch deceiver, however powerful
and deceptive he may be.
Indubitable truth is truth which can not possibly be false. Can
such a truth be found entirely through the use of reason?
Descartes' object through all of this systematic expulsion of
both former beliefs and the sources of former beliefs was his
application of the method discussed earlier. Remember he said
that we must return to the simple, an uncomplicated, non complex
truth which cannot be denied. All of the previous assumptions by
which he lived his life he found were based on ideas that could
have been false. Either he could have been mistaken about them
or a malicious evil genius could have fooled him into believing
them. So he went on.
I myself, am I not at least something? But I have already
denied that I had senses and a body. Yet I hesitate, for
what follows from that? Am I so dependent on body and
senses that I cannot exist without them? But I was
persuaded that there was nothing in all the world, that
there was no heaven, no earth, no minds, nor any bodies; was
I then likewise persuaded that I did not exist?
You should be able to see the problem here. How can he persuade
himself that he does not exist, if he does not exist? Perhaps
not, but what of the evil deceiver?
But there is some deceiver or other, very powerful and very
cunning, who ever employs his ingenuity in deceiving me.
Then without a doubt I exist also if he deceives me, and let
him deceive me as much as he will, he can never cause me to
be nothing so long as I think I am something.
The idea that it was possible for one to think and at the same
time not exist, then even considering all of the conditions he has
put before it, it would still lead to a manifest contradiction. This
was not a new idea in Christian thought. Augustine said it a
little differently, he said that if I think and am mistaken then
I must exist. For him it was a direct refutation of the skeptics
who claimed that one could know nothing for certain. Thinking
implies that something that thinks exists because thinking is an
act of something capable of thought. Aristotle said that the
mind is made up of thoughts and comes into being the moment it
begins to think. In Aristotelian terms, then, existence is
necessarily predicated of anything that thinks simply on the
basis that it is thinking. However, for Descartes a retreat beck
to Aristotle and Augustine was not necessary because the very
idea of non-existence of something that is thinking implies an
unquestioned contradiction. His conclusion, then, is that single
indubitable truth on which he was going to build a total science
of truth. I think therefore I am, in Latin cogito ergo sum.
However, the only truth determined by this is that he was a thing
that thinks in Latin, res cogitans.
Through our senses we see, feel, smell our bodies and the world
that surrounds us. But we have already determined that we have
reason to doubt our senses since we may be sleeping, our senses
may be distorted through illness or circumstances, or a
malevolent demon may be fooling us concerning what it is that we
think we sense. Our bodies and the world around us may not exist
at all. We have not determined at this point any logical
connection at all between us as things that think and the
environment around us as things that exist. However, since we
are things that think we cannot deny that we have thoughts, we
only know that they may not be veridical. Therefore, if it is
possible for us to know our bodies and the things that exist in
our environment, that is know them without question, we cannot
know them through the senses. We can only know them through
What is the relationship between thinking and experiencing? More
importantly can that relationship be determined directly from the
single fact that he exists because he is thinking. Again, one of
his assumptions was that what one is thinking of cannot be wrong.
A person cannot be wrong about what he is thinking of unless he
attempts to maintain that it is equivalent to something existing
outside the mind.
Descartes explained this through a meditation on a piece of bees wax.
This wax, fresh from the hive, still had the color and odor of
honey. It had a distinctive shape. One could knock on it and it
produced a sound. Over time, as it set by the warm stove, it
lost its odor then its color. The wax softened and lost its form
and texture. Yet it still remained the same piece of wax that
was originally taken from the hive. However, we do not know this
by the use of our senses, we know it only through our
understanding. Thus knowing about the wax has nothing to do with
its sensible qualities. The point he is making is that the
sensual qualities of anything may very well be misleading, but
its existence is not. Thus a substance is what is. Aristotle
said that a substance was something you could talk about, an
individual thing of which other things could be predicated but
could not be predicated to anything. For Aristotle substances
were not first principles, we could know nothing about them other
than what was generally predicated of them. Descartes' concept
of substance is a new idea, adapted from Late scholastic thinkers
like Suarez, but more platonic in the sense that it tended to be
a universal concept of being, an idea that would have been
rejected by Suarez. What could be predicated of Descartes'
substance was existence itself. As we can see now, since he has
determined through his systematic doubting that he exists as
something that thinks, he too is a substance, something that has
existence. But in this case he is a mind. There is a difference
between a mind and a piece of wax. The wax is extended in space,
it is corporeal. A mind, on the other hand, is not extended in
space. It is incorporeal. Thus there are two kinds of
substances, mind which is spiritual, not extended in space, and
body, which is corporeal, extended in space.
But what of things that exist in the world? We do, therefore,
have clear and distinct ideas of the existence of some things in
the world. This does not imply that we would not be mistaken
concerning what they were, only that we recognize that other
things exist. Once stub your toe on a stone and the non-existence of the stone is a contradiction even if you did not see
it. It is so even if you did not realize what it was. To know
that something exists, that it is a substance, is to know only
that and no more. It is not something that can be determined by
the senses. It is something that can only be determined by the
The existence of anything implies that it had a cause, that it
was created. What is created must have been created by something
more perfect than it itself is. In order to prevent an infinite
regress there must be a first cause and that first cause must be
more perfect than anything that has been created. This, of
course is God. The question this brings up is that if God, the
infinite craftsman, made the things of the world and if these
things are not perfect, then doesn't this imply an imperfection
in the craftsman? However, if we return to the idea that God is
both perfection and pure being, then we should be able to
envision nothingness or non-being as pure imperfection or error.
In a purely platonic sense, then everything that exists does so
by participating in both existence measured as degrees of
perfection and in nothingness, as measured by degrees of pure
error. This is Descartes' answer to the problem of the imperfect
world as a creation of a perfect God. This is a problem that set
Spinoza and later Leibniz off on new explanations of God and
existence. Thus degrees of perfection are measures both of the
participation of individuals in the perfection of God and of our
own clear and distinct ideas of their existence.
The problem of existence posed another problem for Descartes.
Considering that he lived during a period when the general
cultural view of the world was a kind of machine where everything
that occurred did so through some kind of mechanical operation,
his proposal that there are two kinds of substances, spirit or
mind, and material or body, how is it possible that a spiritual
soul can act on a material body? Descartes used the terms mind,
soul, and self as essentially synonymous. This implies that
passions of the mind that are caused by outside events as well as
willful acts that result in bodily movements require some sort of
mechanical connection between the spiritual soul and the material
body. In his attempt to explain how this can occur, he began by
making a distinction between functions
attributed to the soul and those attributed to the body.
As to this we shall not find much difficulty if we realize
that all that we experience as being within us, and that to
observation may exist in wholly inanimate bodies, must be
attributed to our body alone; and, on the other hand, that
all which is in us and which we cannot in any way conceive
as possibly pertaining to a body, must be attributed to our
Descartes was impressed by Harvey who had recently discovered the
circulation of the blood through the body.
Descartes description of the inner
operations of the body were done with due consideration to
Harvey's work. As an addition to Harvey's description of the
role of the heart and blood he added this description of the
actions of muscles.
We further know that all the movements of the members depend
on the muscles and these muscles are so mutually related one
to another that when one is contracted it draws toward
itself the part of the body to which it is attached, which
causes the opposite muscle at the same time to become
elongated; then if at another time it happens that this last
contracts, it causes the former to become elongated and it
draws back to itself the part to which they are attached.
We know finally that all these movements of the muscles, as
all the senses depend on nerves, which resemble small
filaments or tubes, which all proceed from the brain, and
thus contain like it a certain very subtle air or wind which
is called the animal spirits.
It is these animal spirits that become the vehicle for
communication between the spiritual soul and the material body.
Descartes said that blood in the cavities of the brain form the
animal spirits. "...what I here name spirits are nothing but
material bodies and their one peculiarity is that they are bodies
of extreme minuteness and they move very quickly like the
particles of the flame which issues from a torch." Thus the
reason some muscles contract while their opposites elongate is
that these spirits issuing from the brain cause other animal
spirits in the muscles to move very quickly from one muscle to
When we sense objects in the external world then the senses
themselves, being attached to the brain by the nerves, cause
motions in the brain corresponding to the sensations. These
motions themselves can cause motions in the animal spirits such
that our muscles act without our willing them to do so. Thus it
is possible for the members of the body to act in deliberate ways
without the intercession of the soul. The result of this line of
reasoning is that we can see that there is nothing that we need
to attribute to the soul other than thoughts, which he claims are
of two sorts, actions, and passions.
Those which I call its actions are our desires, because we
find by experience that they proceed directly from our soul,
and appear to depend on it alone: while, on the other hand,
we may usually term one's passions all those kinds of
perceptions or forms of knowledge which are found in us,
because it is often not our soul which makes them what they
are, and because it always receives them from the things
which are represented by them.
This relationship between actions and passions causes a constant
conflict between the soul and the body. The seat, or center of
operation, of the soul, he said, is a small gland in the center
of the brain he called the "pineal gland". This small gland is
nudged around by the animal spirits from the outside which
accounts for the passions, and in turn it pushes against the
animal spirits which accounts for the actions of the soul. This
may seem with our twentieth century background to be a bit
strange. But, remember that this is the early seventeenth
century. Forces which act other than by pushing were unheard of.
They would be considered occult. This also results in a
description of human psychology that emphasizes the new
scientific concept of efficient rather than final causes being
the important causes of events. The Greek way of thinking of the
struggle of the soul as a struggle between the divine soul and
the evil body through Descartes became a mechanical process.
This Cartesian hybrid of religion and science became the basis
for the new synthesis of philosophy and science that was to sweep
the western world, even if only for a short period of time.