Hi! I’m Antonio and
lot of philosophy.
NO WAY! Hi! I’m Amanda and I don’t like to
philosophy except for the existence of God
NO WAY! Hi! I’m Michael
and I like the God
debates. Out of everything in this class I like Plato
NO WAY! I’m
Neil and I’m in a platonic relationship
Existence of god
French philosopher, mathematician and
(optics, physics, physiology)
Father of Modern Rationalist Philosophy
Initiates intellectual break with ancient and
Appeals to analytical reason and logic to
investigate the nature of both mind and nature in
the context of developing science
1543)Astronomy: Heliocentric solar system;
Challenge to Church
endorsed Geocentric universe
1626)Development of the scientific method
1642) Mathematician, Physicist & Astronomer;
Copernican; challenge to Church
1630)Discovered laws of planetary motion
1662) philosopher, mathematician
Baruch “Benedict” Spinoza
1691)Developed experimental chemistry; worked in
mechanics, medicine, hydrodynamics
n (English; 1642
1727) Fundamental laws of physics; classical
Gottfried Wilhelm Leibniz
1650, born at La
, a small town in Touraine, France.
Educated at a Jesuit college of La Fleche. He was dissatisfied with the course of
instruction because it chiefly consisted of the transmission of the received opinions.
1619 in a series of dreams Descartes was convinced that he was favored by God,
destined to be a philosopher.
These dreams motivated him to invent a method of formal reasoning that would
unite both mathematics and the physical sciences.
1637 he published
Discourse on Method.
1640 he grievously experienced the death of his 5 yr. old illegitimate daughter
1641 he published
Meditations on The First Philosophy
with six sets of
objections from various distinguished persons (including Hobbes and
Descartes’ Replies to the Objections
1644 Descartes published
Principles of Philosophy
1649 he became (with much hesitation) an instructor to Queen “King”
Christina of Sweden.
1649 He published
The Passions of the Soul
Feb. 11th, 1650 he died of pneumonia as a result of the
Swedish climate and demands made upon him by the Queen.
Rules for the Direction of the Mind
Discourse on the Meth
Meditations on First Philosophy
Principles of Philosophy
Comments on a Certain Broadsheet
The Description of the Human Body
Passions of the Soul
Existence of God (III)
Vs the evil demon/genius
is the view that "regards reason as the chief
source and test of knowledge" or "any view appealing to reason as a
source of knowledge or justification." More formally, rationalism is defined
as a methodology or a theory "in which the criterion of the truth is not
sensory but intellectual and deductive." Rationalists believe reality has an
intrinsically logical structure. Because of this, rationalists argue that
certain truths exist and that the intellect can directly grasp these truths.
That is to say, rationalists assert that certain rational principles exist in
logic, mathematics, ethics, and metaphysics that are so fundamentally
true that denying them causes one to fall into contradiction. Rationalists
have such a high confidence in reason that proof and physical evidence
are unnecessary to ascertain truth
in other words, "there are significant
ways in which our concepts and knowledge are gained independently of
sense experience." Because of this belief, empiricism is one of
rationalism's greatest rivals.
Brain in a Vat
Can I be a mind/brain without a body?
“But what then am I? A thing which thinks. Whaat is a thing which
doubts, understands, conceives, affirms, denies, wills, refuses, which
also images and feels”
“Thingness” or “identity”
Kinds of Substance
Essence = to be in space without
Ex: A flag
Essence = to think without being in
Ex: The colors of a flag
11. Let us now accordingly consider the objects that are commonly thought to be
[the most easily, and likewise] the most distinctly known, viz, the bodies we touch
and see; not, indeed, bodies in general, for these general notions are usually
somewhat more confused, but one body in particular. Take, for example, this piece
of wax; it is quite fresh, having been but recently taken from the beehive; it has
not yet lost the sweetness of the honey it contained; it still retains somewhat of
the odor of the flowers from which it was gathered; its color, figure, size, are
apparent ( to the sight ); it is hard, cold, easily handled; and sounds when struck
upon with the finger. In fine, all that contributes to make a body as distinctly
known as possible, is found in the one before us. But, while I am speaking, let it be
placed near the fire
what remained of the taste exhales, the smell evaporates, the
color changes, its figure is destroyed, its size increases, it becomes liquid, it grows
hot, it can hardly be handled, and, although struck upon, it emits no sound. Does
the same wax still remain after this change ? It must be admitted that it does
remain; no one doubts it, or judges otherwise. What, then, was it I knew with so
much distinctness in the piece of wax? Assuredly, it could be nothing of all that I
observed by means of the senses, since all the things that fell under taste, smell,
sight, touch, and hearing are changed, and yet the same wax remains. [
I can conceive of my mind as
existing only if I also conceive it
So, thought is an essential
attribute of my mind
But I can conceive of my mind as
existing without an extended
Arguments for Dualism
The dream argument
1. I often have perceptions very much like the ones I usually have in sensation while I am dreaming.
2. There are no definite signs to distinguish dream experience from waking experience.
3. It is possible that I am dreaming right now and that all of my perceptions are false
Descartes realizes that someone may not accept that all of the elements of our dreams may be illusory, so
he introduces another mechanism to increase the scope of our doubt.
The deceiving God argument
1. We believe that there is an all powerful God who has created us and who is all powerful.
2. He has it in his power to make us be deceived even about matters of mathematical knowledge which we
seem to see clearly.
3. It is possible that we are deceived even in our mathematical knowledge of the basic structure of the
For those who would hold (as Descartes himself will later) that God would not deceive us, Descartes
introduces an evil demon instead.
The evil demon argument
1. Instead of assuming that God is the source of our deceptions, we will assume that there exists an evil
demon, who is capable of deceiving us in the same way we supposed God to be able.
Therefore, I have reason to doubt the totality of what my senses tell me as well as the mathematical
knowledge that it seems I have.
Since the source of our knowledge cannot lie in the sense, Descartes must find a way to rebuild the edifice
of knowledge upon material he can find within the contents of his own mind. The first thing he can be sure
of on the basis of this alone is his own existence.
The dream argument
How do you know
which is Real?
The argument for his existence (The "Cogito"
1. Even if we assume that there is a deceiver, from the very fact that I
am deceived it follows that I exist.
2. In general it will follow from any state of thinking (e.g., imagining,
sensing, feeling, reasoning) that I exist. While I can be deceived
about the objective content of any thought, I cannot be deceived
about the fact that I exist and that I
to perceive objects with
certain characteristics. (The famous statement of this from D.'s
Discourse on Method
Cogito ergo sum
." or "I think, therefore I
3. Since I only can be certain of the existence of myself insofar as I am
thinking, I have knowledge of my existence only as a thinking thing (
This shows that the contents of the mind are more easily known than the
The Argument that the Mind is More Certainly known than the
It is possible that all knowledge of external objects, including my
body, could be false as the result of the actions of an evil demon. It
is not, however, possible that I could be deceived about my
existence or my nature as a thinking thing.
Therefore, our mind is much more clearly and distinctly known to us
than our body.
Descartes still has no knowledge of anything outside of his mind. He
still has to make the crucial leap to the existence of an object
outside of his mind. He must do this, however, strictly on the basis
of the contents of his own mind. It is the idea of God that he finds in
his mind that allows him to make this leap, and which forms the
basis for his knowledge of all other external objects.