1. First Meditation – paragraph 1
What problem troubles Descartes?
falsehoods from childhood, doubtful edifice based on them
What is his ultimate goal?
establishing something stable and lasting in science, finding something certain
What is his method for achieving this goal?
demolishing every opinion

2. ¶2 – Clarifying the method
How to demolish all my opinions
Do I have to show that they are false? No.
I just have to find some reason for doubt (i.e., show that they are less than certain)
Do I have to examine and reject every single opinion? No.
I just have to examine and reject the foundational opinions (and then all the others will ‘collapse’).
Apparently, rejecting an opinion is merely withholding assent from it.
He’s not rejecting this opinion as a falsehood, he’s just not going to accept it as true.

3. ¶3 – Sense-based opinions
Take the opinions I am most confident about—how did I get these opinions?
From the senses (eyes, ears, )
But should I completely trust my senses?
No, because they can deceive us (at least occasionally).

4. ¶4 – Indubitable beliefs?
But wait a second!
Sure, our senses can deceive us about things far away or in poor light.
But some of my sense-based beliefs cannot be doubted.
ordinary beliefs concerning my immediate surroundings or my own body
Or at least the only way to doubt them is to model myself on insane people.
And modeling oneself on the insane is itself insane.
I mean, right??

5. ¶5 – Dreaming
Ah, but when I’m asleep, I have experiences just like the experiences of insane people (and sometimes even crazier).
Sometimes these experiences deceive me about my immediate surroundings.
I think I’m awake in front of the fire, but really I’m asleep and dreaming.
[So, even with beliefs about my surroundings, perhaps there is some reason for doubt]

6. ¶5 – Dreaming
But right now, aren’t there some sure signs that I’m awake?
wide-open eyes, head feels awake, deliberate movement, clarity
No, because such thoughts have deceived me before.
There are no sure signs for settling whether I am awake or dreaming.

7. ¶6 – Dreams and paintings
But even if I am dreaming, still the contents of my dream must be based on things that are real.
Just like how a painting of something unreal must be based on real things.
Or even if the dream is extremely alien and exotic, still it must at least be made up of materials found in reality.
Just like how any painting, no matter how alien and exotic, must at least make use of colors.
So even if I am dreaming, still there must be some simple and universal things that are real.

8. ¶7 – Simple and universal things
Things like:
corporeal nature and its extension (matter and the way it takes up space)
shape of extended things
quantity, size, number of extended things
space
time
These are the most basic elements of the world; everything is made out of them; and even if I am dreaming, still these things must be real.

9. ¶8 – Science and mathematics
So the dream argument undermines science, but leaves math safe.
Studies of composite things are doubtful.
Physics, astronomy, medicine, . . .
But studies of simple things might still be safe.
Geometry, arithmetic, . . .
Whether or not I am dreaming, still = 5 and squares have four sides.

10. ¶9 - God But I believe that God made me the way I am.
So perhaps I am deceived about shape, size, place, and the like, because of the way God made me.
And perhaps I go wrong even when I try to do simple mathematics, because of the way God made me.
Maybe I’m deceived even about these simple and universal things!

11. ¶9 - God
Objection: But if God is good, how could he allow me to be so radically deceived?
Response:
I already think that, even though God exists, still I am deceived at least occasionally.
And since it’s consistent with God’s goodness to allow me to be occasionally deceived, it must be consistent with God’s goodness to allow me to be radically deceived.

12. ¶10 – Atheism? Perhaps there is no God.
But if so, then the original cause of my existence would be something like fate or chance or a long causal chain.
So my original cause would be less powerful.
Which makes it more likely that I am flawed, and prone to deception and error.
So now it’s even more likely that I’m deceived all the time.

13. ¶10 – Universal doubt
So, for each of my beliefs, there is a legitimate basis for doubt.
This includes beliefs about my immediate surroundings, about my own body, about basic elements of reality, and even about mathematics!
I want to discover certainty.
So I must try to withhold assent from each of my former beliefs.

14. ¶11 - Habit But it’s so difficult to stop believing them!
Old habits die hard. Effort is needed.
Even though I recognize that they’re not completely certain, I still think they’re probable.
So I’ll have to pretend that they are false.
This goes further than mere withdrawal.
This will keep old habits from interfering with my intellectual project.

15. ¶12 – Evil demon
So I’ll suppose that an all-powerful evil demon is trying to deceive me about everything.
Everything I experience is an illusion.
And I will refuse to believe the illusions the demon is creating.
Though I can’t know any truth, I can at least avoid falsehood.
This is very difficult to maintain. It’s easy to slide back into my old opinions, my familiar illusions, instead of facing up to the intellectual problems I’ve raised.

16. Questions
When Descartes doubts all his beliefs, what exactly is his attitude towards them?
What is the Deceptive Senses argument supposed to show?
What is the Dream argument supposed to show?
What is the point of the ‘dreams and paintings’ analogy?
What is the God argument supposed to show?
Why does Descartes introduce the evil demon scenario?

17. Tougher questions
If we can’t be certain about math, then presumably we can’t be certain about logic. But then how can Descartes reason his way out?
When Descartes pretends that his former beliefs are false, is he accepting their negation? If so, doesn’t that contradict his method of rejecting all uncertain beliefs?
Why doesn’t the Dream argument raise doubts for math?