Rene Descartes and Rationalism - Bayt al
Transcript Rene Descartes and Rationalism - Bayt al
Rene Descartes and
Lecturer: Dr. F. Budi Hardiman
1596: born on 31st March in La Haye
1604: entered the Jesuit College in La
Fleche, studied natural sciences and
philosophy of scholastics i
1613: studied law Poitiers
1615: studied mathematics in Paris
1617: Military service in Bavaria,
1621: Traveled to Swiss, Poland, Italia
1625: lived in Paris
1629: emigrated to Netherland
1637: published Discours de la
1641: published Meditationes de prima
Philopophia, debated with Gassendi,
Hobbes and Mersenne
1644: published Principia Philosophiae
1650: was dead in Stockholm
Le doute methodique
• Method is rule that can be used to find
the solid foundation of our knowledge.
• Descartes tried to find this absolute
foundation that cannot be shook by mere
opinions or claims of belief
• His method was unique and has not been
practiced in the history of western
philosophy – the method of doubt
What happens, if I doubt
• Our knowledge comes from tradition, authority,
socialization etc. Is it fictitious or real? If we
doubt the mathematical axioms, metaphysical
claims, religious beliefs or everything in our
experience or sense of perception, then we stay in
an situation in which we loss all certainty. The
dream or fiction cannot be differed from the
reality. Descartes provoked us to assume that the
material world is only an impression that is
produced by a ‘genius malignus’ (an intelligent
Cogito or The Result of the
Doubt about the Doubt
• If we doubt everything, i.e. the material
world outside or the spiritual world inside,
we reach the point in which “we are
doubting” cannot be doubted anymore. So,
the fact that we are doubting is not
doubtful, but certain. It is not refutable.
• Descartes concludes that “I doubt” or “I
think” (Latin: cogito) is the certain and
solid foundation of our knowledge.
Je pense donc je suis
• “I think” cannot be refused. It means
also that “I think” exists. In other
words, my consciousness that I am
thinking now demonstrates that I
exist as a thinking being. Descartes
says shorter: Je pense donc je suis (I
think therefore I am/ Cogito ergo
The Consequences of the
These on Cogito
• The reality outside of us is constructed by our
thought. As a construction of our consciousness it
depend on our subjectivity.
• The reason, i.e. our faculty of thinking, is the only
source of human knowledge. It is a priori in
character, i.e. the knowledge does not come from
the experience, but from the logical principles of
• These consequences are very critical, because
they test belief, dogma or authority under the
control of reason.
The Doctrine of Innate
• Where do the “I think” come from?
Descartes answers this question that 
the faculty of thinking is inherent to us. It
is an innate idea that we have since we
• There are another innate ideas, i.e.  the
idea of extension through which we know
our body and the material reality outside
of us and  the idea of God by which we
strive to perfection.
The Doctrine of
• The three innate Ideas, i.e. thinking, extension
and God, are not only inside of us, but they stand
also outside of us. Because our thought, i.e. the
idea, constructs the external reality.
• So, Descartes teaches us that there are three
substances or kinds of reality outside of us, i.e.
res cogitans (or thinking thing), res extensa (or
expanding thing) and God. The three substances
are not only in our though as ideas, but also exist
outside of us as realities.
The Existence of God
• God is an innate idea. We can think of God
because of this idea. But God is not only in us, i.e.
in our thought. He exists outside of us. This
argument that concludes the existence of God
from the fact that we have an a priori knowledge
of God is called “ontological argument”.
• This evidence of God existence through
ontological argument can be traced back to the
British medieval philosopher Anselmus of
Religion and Philosophy
• Cartesian View of the existence of God show us
the role of philosophy to approach the religious
phenomenon rationally. Philosophy has no claim to
substitute the religion. It tries to understand the
religious phenomenon with our reason. But what
for? It is right that the religious phenomenon is
beyond rationality, but the rational understanding
of religion can make the religious experience more
discursive and communicative. And rational
discourse protects us against an absolutization of
subjective religious experience.
God in our
God in the external reality
• Descartes sees the human body as res extensa
that is separate from the human soul or res
cogitans. So, we find here the dualistic view of
man that claims that man consist of two separate
substances, i.e. the material and the mental
• In our body there are a bridge that connects our
body and our mind. It is the ‘glandula pinealis’. The
body is mere l’homme machine (human machine)
and the soul is the steering faculty that is
comparable to a captain that steers the ship.
Body and Soul
• Cartesian view on the relation between
body and soul approaches the Platonic
dualism. According to the body and soul
dualism our body is material in character,
whereas our soul is spiritual and eternal.
The soul takes control over the body
• World religions still believe in this kind of
Critique on Descartes’
• Is it true that what we think can be
found also in the external reality? A
picture does not always correspond
to the picture object and vice versa.
This bridge problem shows the basic
difficulty in the cartesian philosophy.
• According to cartesian View of Reality the
objective world is a rational entity that
can be known by means of our rational
consciousness. So, the history of modern
philosophy begins with a optimism that the
human reason can grasp the reality.
• Descartes is the father of modern
philosophy and the forerunner of
The other Rationalist
• Baruch de Spinoza: monism and pantheism
– the being as single substance
• Leibniz: pluralism – the reality consists of
multitude tiny units called “monads”.
• Pascal: le coeur a ses raison que la raison
ne connait point – le pari
Newton and Modernity
• Newton influents deeply the modern
thought. The thinker such as Leibniz
assumes the mechanistic world view
that bases the modern physics.