The Basics: Some Familiar Territory
Plato’s knowledge as memory,
learning as remembering.
Innate ideas.
A priori knowledge.
Logical “truths” that describe
phenomena of the physical
world (“A or not-A:” “The door is
either locked or not-locked.”)
The Historical Context
@ 400 BCE: The Greeks
Plato , Aristotle, Pre-Socratics
1600-1800 CE: The Renaissance
Descartes, Spinoza, Leibniz
Collapse of palace-centered
economies.
Waning authority of the Church.
New commercial classes.
Schisms (1378-1417).
New democracy.
Established power supported by
old mythos replaced by new
power based on logos.
Need for new order (Plato’s
metaphysics).
Protestant Reformation (1517
Luther’s 95 Theses).
New sciences (Newton, Kepler,
Galileo, Copernicus).
Nickolaus Copernicus (1473 – 1543 Poland)
If all the planets orbit the sun,
including Earth, then the human
drama is not really at the center of
God’s attention (human dignity?).
But, thankfully, the moon clearly
orbits Earth.
Galileo (1564-1642 Italy)
The Inquisition:
Explain Yourself
If Jupiter has
moons that
orbit it and not
Earth, then…...
The Sentence: Life
imprisonment (at
home)—dies 5 years
later.
What does this have to do with Rationalism?
Descartes (1596-1650
France).
Practicing Catholic.
Just sent manuscript of The World
to publisher (contained ideas that
mirrored Galileo).
Worried about the ability of
oppressive, unbending religion to
survive the challenge of science.
Hmmmm…..If I could only think of a way to continue
exploring science without infuriating the Church
What if I could
show that science
itself depended on
some theological
principles that
recognize the
authority of the
Church?
Where Descartes’ Path Led Him
How can Descartes reclaim
the world (and science)?
If there is an all-powerful,
all-knowing, all-good God,
then an evil genius cannot
be calling all the shots.
If an evil genius isn’t totally
controlling me, then it is
possible to find other
truths.
The Challenge
Can’t use math, can’t use
body, and can’t rely on
sense data about the
world.
God must be found in a
priori knowledge.
Step 1: Establish the Primacy of Some Innate Ideas
Wax appears….
Wax smells….
Wax feels….
Wax sounds…
Wax tastes….
Is it still wax?
Is it the “same” thing?
From where does the idea
of “thingness” or
“substance” come?
The Implications
Sameness or identity is a priori
knowledge (A=A).
Substance is a priori knowledge.
From Meditation I: Self is a priori
knowledge.
Descartes is
“modern” in
his reliance on
reason over
authority.
Descartes’ 1st Argument: Argument from Perfection
A being that doubts is an
imperfect being.
I doubt; therefore, I am an
imperfect being.
Yet I could know that I am
imperfect only by having
the concept of perfection.
Therefore, I do have the
concept of perfection.
I could not have received the
concept of perfection from
something imperfect;
therefore, my concept was
not derived from myself.
Therefore, my concept of
perfection was derived from
something that is perfect.
Only God is perfect (i.e. God is
perfection), so I derived my
concept of perfection from
him.
Therefore, God exists.
So…….
If God exists, I am
not possessed by an
evil genius.
Science safely rests on a godly foundation, and
the soul is safe from science since the soul
cannot be observed and measured.
Problems for Descartes
“Commonsense”
experience of reality
doesn’t work.
Cartesian experience of
reality is counterintuitive.
And More Problems….
If substance is “absolutely
independent,” then how
can there be both an
infinite substance and finite
substances?
How do the mind and body
substances interact?
Baruch Spinoza (1634-1677 Amsterdam)
Like Descartes’ idea of
substance, but not the
contradiction between
infinite and finite
substances.
So what if God were the
only substance?
Spinoza: “Nature equals God” (pantheism).
All things are
expressions of
God.
One must love
all things to
love God.
To love God is
to have
knowledge of
him.
Gottfried Leibniz (1646-1716 Germany)
Didn’t like Spinoza’s
pantheism and
immanent God.
Wanted a return to
Descartes’ transcendent
God (without Descartes
errors).
Leibniz’s Principle #1: Principle of Identity
All bachelors are men.
The cat is on the mat.
2+3=5.
Obama is president of the US.
Either A or not-A.
Leibniz is dead.
Leibniz’s Big Move: Sub Specie Aeternitatis (consider it
from Gods’ point of view)
If God is omniscient,
omnipotent,
omnipresent, and
perfect and if God has
a plan, then synthetic
propositions are
necessarily true from
God’s point of view.
Leibniz’s Principle #2: Principle of Sufficient Reason
Anything that exists exists
for a reason and exists as it
does for a reason.
God saw all possibilities at
the moment of creation
and chose what and how to
create.
God makes no mistakes and
leaves nothing to chance.
The sky is blue because God made it
that way.
John is talking to his philosophy class
about Leibniz right now because God
made the world in a way that requires
John to be talking to the philosophy
class about Leibniz right now.
What does this mean?
Just as “2+3=5” is
necessarily true, so is
“Obama is president of
the US.”
It can’t be any other way.
The cat is on the
mat…..and IT HAS TO BE.
Leibniz’s Principle #3: Principle of Internal Harmony
An omnibenevolent God
wants….
Maximum existence
(Metaphysical Perfection).
Maximum Activity (Moral
Perfection).
God considered all
possibilities & arranged the
individual parts to
harmonize.
World may appear imperfect to us,
but it could be worse.
In what ways are Descartes, Spinoza, and Leibniz telling
us about the nature of reality and the world “out
there”?
Descartes and physical
laws.
Spinoza and unity
Leibniz and coherence
Origins of Perfection
Infinity, Eternity, Circle,
Equality, etc.?
Sense data does not
provide for knowledge
and certainty?
Logic and reason tells us
about the world “out
there”?
Strengths of the rationalist
approach?
Weaknesses?