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What can I know with certainty?

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Tyler Zimmer

on 23 January 2017

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Transcript of What can I know with certainty?

What was Descartes's main goal or aim?
What was he reacting against?
How did he proceed (what was his
Meditation 3
1. Move beyond knowledge of the contents of our own mind.
2. Establish a way of reliably gathering knowledge of the external world, of other minds.

Image by Tom Mooring
"The Cogito"
"Cogito ergo sum"
I think, therefore I am
The Cogito
"I think, therefore I am" is the
first truth
that we reach by philosophizing in an orderly, rational manner.
It is always available to us, no matter what.
It, Descartes argues, is exactly what we've been looking for: a
rock-solid, indubitable foundation for scientific knowledge.

In the very act of doubting, my own existence is revealed... we must exist in order to be deceived, to dream, to be in the matrix, to doubt, etc.
Descartes's Goals
Wanted to break with what he saw as unreliable, unproductive traditions.
Wanted to wipe the slate clean:
...sweep away prejudice, superstition, error, bias, etc.
...sweep away wooden orthodoxy.
...leave only what truly deserved to claim the mantle of
scientific knowledge

What can be called into doubt
Meditation 2
Rene Descartes (1596-1650)
What are some different ordinary sources of knowledge we rely on in daily life?
Everyone has had the experience of coming to realize that they once held a false belief. If you had to generalize, what would you say the main sources of error or false belief have been in your life?
Descartes on what motivated him:
"Some years ago, I was struck by the large number of falsehoods I had accepted as true in my childhood and by the highly doubtful nature of the whole edifice that I had subsequently based on them.
I realized that it was necessary once in the course of my life to demolish everything completely and start again right from the foundations
if I wanted to establish anything in the sciences that was likely to last..."
Our minds have been
and this has ongoing bad effects on our lives.
Our minds, therefore, must be
, and then restocked with nothing but rational, reliable beliefs of which we can be certain.
We need a
new method
---a rational, scientific one that gives us a solid foundation on which to build.
We need a
rock-solid foundation
for knowledge in order to lay a sound basis for modern science.
Knowledge is like a multi-storied building: the upper floors rests on the bottom floors, all rests on the foundation.
A rotten foundation undermines the entire structure.
Medieval ("Scholastic") philosophy
Religious Orthodoxy
Authority of Church, of economic elites
Uncritical thinking, superstition prejudice, bias, error enshrined in "tradition."
The Case of Galileo
Using observation, telescopes, mathematics, etc. he discovered that, contrary to the orthodoxy of the day, the earth actually revolved around the sun and not the other way round.
He was persecuted, attacked, imprisoned, punished.
Modern Ideals:
"Naturally subordinate"
"Natural authority"
"Natural experts"
To be "modern" is to begin to question the following ideas:
Descartes was criticized for being an atheist, even though he was not.
He was accused of being
Why do you think some groups had this reaction to Descartes?
Who do you imagine the groups most threatened by him were?

To what extent is Descartes's project still "dangerous" or "subversive" today?
Descartes' Method
Rather than relying upon the say-so of authorities, Descartes created a method that anyone could use that relied upon nothing but
We might call his method:
, and
Basic goals of Meditation 1
1. Use method of radical doubt, Clear away error, wipe slate clean.
2. See if anything remains.
Lead-in to First Meditation
Our minds have been
. We need to purify ourselves of error, superstition, etc.
But how should we proceed?
"Here I shall employ an everyday example to explain my procedure... Suppose you had a basket full of apples and, being worried that some of them might be rotten, wanted to take out the rotten ones to prevent the rot from spreading. How should you proceed? Would you not begin by tipping the whole lot out of the basket? And would not the next step be to cast your eye over each apple in turn, and pick up and put back in the basket only those he saw to be sound, leaving the others? In just the same way, those who have never philosophized correctly have various opinions in their minds which they have begun to store up since childhood, and which they therefore have reason to believe may in many cases be false. They then attempt to separate the false beliefs from the others, so as to prevent their contaminating the rest and making the whole lot uncertain. The best way to accomplish this is to reject all one's beliefs in one go, as if they were
uncertain and false. They can then go over each belief in turn and re-adopt only those which they recognize to be true and indubitable.."
Radical Doubt
Criticism by Charles Peirce
"Some philosophers have recommended that we begin our studies by questioning everything. But the mere putting of a proposition into the interrogative form does not stimulate the mind to any struggle after belief. There must be a real and living doubt, and without this all discussion is idle...
Let us not pretend to doubt in philosophy what we do not doubt in our hearts
." - Peirce, "The Fixation of Belief" (1896)
First Meditation
Common sense teaches that all knowledge is based on
sense experience
. So this is where Descartes begins.
We are looking for a 100% reliable foundation, something that is absolutely certain that we could never be wrong about.
The senses cannot serve as this foundation because they are not 100% reliable; they sometimes lead us astray.
Math can't serve as a foundation
Either we were created by an all-powerful God, or else we were created by humbler means.
If we were created by an all-powerful God, that God could, in principle, do anything, including deceive us systematically.
But if our origins are humbler, we are less perfect beings and are more susceptible to getting things wrong.
Either way, we can't rule out pervasive error.
Thus, mathematical truths may be doubted and cannot serve as our rock-solid foundation.
THE MATRiX (1999)
Which pill should you choose?
What Remains?
The following are not 100% reliable:
Sense perception.
Say-so, testimony.
What we read in books.
What authorities tell us.
Descartes says that he knows with certainty that he is thinking and, therefore, that he exists.
But what happens when we try to doubt that we exist? Is this possible? Is Descartes right about this?
The Cogito
Returning back to
The Matrix
, how does Descartes's "cogito" relate to Neo's predicament?
The Wax Passage
What is Descartes trying to show?
What conclusion is he trying to establish here?
Is his argument convincing?

Where we've been... Where we're heading...
1. We wiped the slate clean with
radical doubt
2. We established that everything could be doubted except one thing:

3. We inferred that, based on the "cogito",
we know our mind better than our senses
or bodies.
4. But the senses still remain in doubt... we know our mind but we're alone and isolated. We have no reliable way, at this stage, of obtaining
knowledge of the external world
1. See if anything can be salvaged after we have employed radical doubt far and wide.
2. Show why, ultimately, the existence of our own mind is the only thing that cannot be doubted.
3. Prove why our knowledge of our mind is more certain and immediate than our knowledge of our body.
Three types of ideas
1. Innate ideas.
2. Fictitious ideas.
3. Adventitious ideas.
1. All ideas must have a cause.
2. I have an
of God as a perfect all-powerful, all-knowing, all-good being.
3. I myself do not have all the perfections that my idea of God represents God as having.
4. Because I am imperfect, I couldn't have been the first cause of this idea of a perfect God.
5. The only thing thing that could have been the first cause of this idea is a perfect being, i.e. God.
Therefore, God must exist.
I doubt, therefore I lack perfect knowledge, so I have some idea of imperfection. But this means I also have an idea of perfection, thus I have an idea of a supremely perfect being, God. This idea must have a cause. But I could not have caused it by myself. Nothing short of a perfect being could explain why I have this idea.
Thus, God must exist necessarily.
Pope John Paul II on Descartes
"though the father of modern rationalism certainly cannot be blamed for the move away from Christianity, it is difficult not to acknowledge that he created a situation in which estrangement became possible... Descartes put to one side the true God---God the redeemer. The consequence was that man was to live by his own reason alone, as if God did not exist."
"Descartes was more interested in 'God the mathematician' and less so in 'God the redeemer."
What kind of insight is the "Cogito"?
The "Cogito" as Foundation
Cogito is first truth we discover when we think critically, rigorously, and systematically.
It is the "foundation stone" for all other knowledge because of its immunity to radical doubt.
Its significance is that we know the facts of our own consciousness and existence with
more immediacy and certainty
than we do the senses.
The Cogito
So far we've doubted almost everything and the
only thing standing is the Cogito
Where does that leave us?
Do we know what kind of a being we are?
Do we know if beings with other minds exist?
Do we know if God exists?
Do we know if the external world exists?
The only thing we can be certain of at this point is that we, as individuals, exist as "thinking things."
It remains to prove everything else.
Where we are heading...
Descartes has disproven the traditional view about the order of knowledge that places the senses at the foundation.
Instead, Descartes argues that we can know the
contents of our own minds
better, more intimately, with more certainty than we know our senses, our bodies, the external world, etc.
The senses are the foundation of all knowledge. We can be surer of our senses than of anything else.
What we can know by internal reflection is the foundation of all knowledge. We know the contents of our own minds with more certainty than anything else.
Descartes's Goal in the "Wax Passage"
Attack empiricism.
Tries to show that all knowledge cannot be based on sense experience.
Without the guidance of our minds (concepts), sense experience alone cannot give us full knowledge of the world.
The Wax Passage
We know that certain things persist even through radical changes.
We know that wax, for example, is hard when cold and liquid when hot. But it's still wax, regardless of what its sensible properties are like.
The "essence" of wax remains constant even through these changes.
Can the empiricist explain how we know what wax is?
Descartes's answer is "no."
We can't grasp the concept of "sameness through change" by way of the senses.
We can't grasp the "essence" of wax by way of the senses.
Thus, the senses can't be the foundation of all knowledge.
What info do the senses give us?
Before we light the candle, how does it feel and look?
What about once we've lit it?
What about once it's completely melted?
Can all of this sense-based information explain how we know the wax continues to exist amidst external changes in its sensible properties?
A Detailed Look
at the Argument
1. Sense perception of wax changes even though wax continues to exist amidst change.
2. The "essence" or "identity" of some object is its unchanging features.
3. When we correctly identify an object in the world, we perceive its essence, not simply its appearance.
4. The senses only give us information on how things appear to our sense faculties.
5. The senses cannot give us knowledge of essences, for that we need the mind.
6. The senses cannot be the foundation of all knowledge, since they depend on the mind in order to give us full knowledge.
OK, so what's the point?
You know you exist, you know you are a thinking thing. The mind alone can uncover the true nature of things, the mind is easier to know than any physical thing.
This enables us to reject empiricism, the "foolish" bias in favor of the senses.
The mind is the most fundamental basis of all knowledge.
Descartes's project is
radically modern

His philosophy embodies the key modern idea that
(not just elites or experts) can discover which beliefs are true (by means of reason alone) without imposition of outside authority.

When we're dreaming, we have elaborate sense experiences. But those experiences aren't of anything real.
This is a case where our senses deceive us; we sense things but they aren't real.
If we formed beliefs on the basis of these experiences they would be false beliefs.
This proves our senses aren't 100% reliable.
The Evil Demon Hypothesis
"The whole argument lies in this: I recognize that it would be impossible for me to have within me the idea of God were it not the case that God really existed."
Be critical.
Don't take the word of authorities for granted, subject all beliefs to rational scrutiny. Think for yourself.
The most fundamental source of knowledge is our mind, our ability to think/reason. The senses are not the most fundamental or intimately known source. (Anti-empiricism).
Knowledge is like a building: it must have a single, rock-solid, absolutely certain foundation or else the whole edifice is shaky.
Cogito ergo sum.
"I think, therefore I exist" is the first truth we reach when we philosophize in an orderly way. We can't doubt our own existence.

Is stealing always wrong?
Imagine that a loved one is very sick and will die unless they get a certain widely available medicine. The problem is this: the medicine is expensive and you don't have the money to purchase it. Time is ticking away. If you could get away with stealing it from a pharmacy, would that be the right thing to do?
What are the relevant variables that we need to consider in this case? In other words, what sorts of things do we need to take into account here to decide what to do? Make a list.
What is the right thing to do in this case? Why? What is your reasoning for course of action?
Is doing the right thing always the same as doing what the law requires? Is it possible for morality and the law to be at odds with one another? If so, what should we do in such cases?
How do we know what morality requires of us? Why should we think morality has any authority over us? Should we obey it?
Is it just for life-saving medicines to be sold as commodities on markets for profit?
Some philosophical problems...
How do we settle disagreements about these sorts of questions?
What is the best method for determining the correct answers to these questions?
Notice his use of first-person, his decision to publish in French, etc.
"I am here quite alone, and at last I will devote myself sincerely and without reservation to the general demolition of my opinions."
Why does Descartes want "generally demolish his opinions"?
Dr. Tyler Zimmer
What we want:
An absolutely certain, rock-solid foundation for knowledge, so each of us as individuals can reliably distinguish between truth and error.
How he proposes to get there:
Using the method of radical doubt, test the sources we rely on to see if any of them can serve as our rock-solid foundation.
Three sources of error
Failure to
of reason.
of reason.
What is the
social and political basis
for these mistakes?
The more
the doubt, the more
is whatever that survives it.
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