Descartes P2

11. Basically Descartes method is to doubt everything until he finds an absolute truth, his justification for this method is that few things can be absolutely known to be positively true or a reliable source for knowledge. One can’t depend on senses, what if you’re dreaming, what if there’s an evil genius tricking us? etc. He couldn’t depend on the knowledge that came before him because he didn’t think it was credible or had a strong foundation for knowledge. He used math as a model to guide him because it’s structure of reasoning was credible enough but not quite to the level of his satisfaction because most things were assumed, then proven. But he did use the same basic form which was step by step reasoning and deduction. He wanted to find an absolute truth that everything else could then stem from forming some foundational structure of knowledge. I don’t think Descartes believes in some things being so obviously true and to not worry about them because he doesn’t take anything for granted and he questions everything. In order for Descartes to produce what he would consider real knowledge he would have to find the most basic and simplest truth that cannot be doubted and base everything else on that.

12. For Descartes our senses were unreliable sources of information because there are times we can misinterpret information through our senses and in a way be tricked by them. Like when you look at a straw in a glass of water it looks crooked or cut in half when in reality it’s straight. If his method is to doubt everything until something cannot be doubted then the senses would fall under the category of things doubtable which means it cannot be used as a source for knowledge.

13. Mathematics derives knowledge based on first principles that can be used to deduce new formulas. This form of knowledge is based on logic and reasoning. But in some forms of mathematics such as geometry the first principles or propositions everything else is based on are just assumed, they haven’t actually been proven. I do not think the truth or falsity of mathematics depends on a particular kind of world because these ideas can still be conceived of within the mind if nothing else existed externally. There are many mathematical formulas with huge numbers that would be impossible to observe all at once through the senses and adequately decipher them first hand but we can intellectually conceive of them without our senses, so in my opinion mathematics is based on logic and can be used to explain the world around and help us understand it. I do not think logic can be doubted in the same degree that senses can be doubted, it is more dependable but Descarte still couldn’t use math as his foundation because there was still room for doubt. He wanted something one couldn’t doubt.

14. His “Cogito ergo sum” came about by Descartes first doubting everything and assuming that he knew nothing. To go even further he presented a hypothetical situation where some evil being was deceiving him in every possible way so because of this he had to question the truth / validity of everything he knew, he took nothing for granted. After examining everything he came across he finally concluded that there was one known fact that could not be a deception and so he could not possibly doubt – that his very thoughts existed and he himself was a thinking thing: “I think therefore I am. “

15. Descartes attempts to show that innate ideas exist. Innate ideas are formed based on internal knowing as the source rather that anything external from sensory information. He explains how this type of knowledge could come about by describing a piece of solid wax through sensory information, then as the wax melts in heat its form changes. Now he can no longer rely on sensory information to know that it is in fact the same piece of wax. It seems the only way to know this without depending on sensory information would be if it was an intrinsic source or innate idea.

16. Descartes “concept of perfection” comes from realizing that there exists some notion of perfection and wonders where it comes from. He rules out the senses as a source because he considers nothing in the world to be perfect. He rules out himself because he doesn’t consider himself perfect due to the fact that he has doubts or in other words he doesn’t know everything. He comes to the conclusion that the concept of perfection must have come from the existence of some perfect being i.e. God with all the perfect God-like qualities. He then uses the existence of God to rule out any such evil deceptive being that could twist our perceptions.


17. Descartes argument for the existence of the external / physical world is based on the previous propositions. If there is an all perfect being then he would not create people with unreliable senses, so our senses our reliable because God is not a deceiver. If the external world did not exist then that would mean our senses were unreliable, and so there could not exist an all perfect being, and so forth the tower falls. So he goes back to the first point of his concept of perfection, if this can be known for certain then everything else should logically follow leading to the existence of the external world based on the reliability of our senses.


This whole thing was very interesting and I did a little extra research on the side to get a better more well rounded understanding of Descartes argument and I think the most interesting thing was his process and how he approached each thing before analyzing it. The wax argument was a little confusing so I attempted to ponder another example of a caterpillar turning into a butterfly. The cocoon would be a safe way to ensure any trickery or deception unless the cocoon was tampered with. Even though the creature has completely changed we are quite certain it is the same entity, and it doesn’t seem to be based on sensory information. Hmm even if it was I still can’t help but wonder if Descartes was right about innate knowledge because of how processes such as logic / reasoning exist at all in the first place as dependable sources for knowledge in math, science, etc. Logic is a tool many people have used in philosophy and there are rules and forms that enable us to reason and discover truth/knowledge. It does not seem to depend on the external world because you could have a very logical argument about unicorns when they don’t even exist, but the form is valid. So what does reason or logic depend on or what is it based on? Does logic itself show there must be some objective truth or innate knowings? If logic does not gain knowledge through the senses than how do we know logic?