The properties of the object: shape, quantity, and size."I may holding a book but this book may not exist and just an illusion from my dream world, But the property of it, this thing must be real." (Projection of greater reality)

Proof of Greater Reality in Dream

Undoubtedle foundational beliefs system demands Certainty as a quality of it.So he generate doubt to the foundation of his old beliefs as many as possible to find something that is Certain. He doubt everything by formulating different Skeptical Hypothesis.

Methods of Universal Doubt 

Rene Descartes still doesn't satisfied about this argument he insisted that even though we are in the world of dreams, we all know that dream is just reflection of the reality or a projection of Greater Reality.

At the end of Meditation One, Rene Descartes is force to consider himself as no eyes, no blood, nor any senses because any of those are doubtable. Therefore, those things lacks the quality of having Certainty.(Rene Descartes continued his Quest for Certainty in Meditation Two)

Then Rene Descartes insist that "what if there is some malignant evil genius exceedingly powerful and cunning. Devoted all of his power to deceived me. I shall supposed that the sky the earth, color, shape, sound, and all external things are illusion imposed by evil demon"

The Evil Genius Hypothesis 

Descartes realized that when he is in the state of having a Dream, he has a perception, at that moment he all of his senses are being deceived as everything in that world of dreams are indistinguishable to the world of reality.Premise 1: We can't always tell when we are dreaming.Premise 2: if we can't tell that we are dreaming, we can't be certain that we are dreaming right now.Premise 3: If we cannot be certain that we are not dreaming right now, then we cannot know anything about the world of reality.Conclusion: We can't know anything about the world of reality.

The Dreaming Hypothesis 

Rene Descartes wants to demolish his old beliefs system and start over again from beginning to established a new falsehood-proof undoubtedle foundational beliefs system as a basis for his new opinion, judgement, and beliefs.

Foundationalism 

Rene Descartes doesn't seem to be satisfied, as this argument only doubt specific senses and at extreme circumstances—objects that are far away, very small, dimly lit, etc. thus, he find a circumstances were all of his senses are deceived.

Rene Descartes doesn't seem to be satisfied about the simple things, he welcomed the possibilities that those properties are also falsehood.

This Evil Genius fed Rene Descartes' experience and make him think that this world and every simple things are real but in reality it is just simulated or a Grand Illusion generated by the demon.Premise 1: I can't rule out the possibility that I am deceived by an Evil Genius.Premise 2: if so, then I can't really know the real world.Conclusion: I can't know anything about the real world.This is the best possible skeptical argument.

He states that "God is all powerful so he could possibly deceived me even in simple things"But then he realized that the God he worship is an All-good being. therefore, that God will not deceived him.

Deception of a Powerful being

Rene Descartes realized a large numbers of falsehood from his opinion, judgement, and beliefs that he had accepted to be true.This raises suspicion about his whole belief system, if some are bad, then others might be too. He also question the foundation of does beliefs since many beliefs have been built on the bad ones.

Introduction 

First, he look at his primary source of his knowledge that he acquired and realized that it came from Experience. Experience relies on senses. he raise doubt to it:Premise 1: My senses sometimes deceive me. (e.g. Paredolia, optical illusion, false perception, etc.)Premise 2: One should never completely trust what once has deceived one. (Cartesian Quest for Certainty Principle)Conclusion: I should not completely trust my senses.

The Perceptual Illusion Hypothesis 

Descartes create a distinction about different thingsComposite things - are the things that are complex, always changing, dubious and must be doubt like Physics, Astronomy, and Medicine.Simple things - are the things that are fixed and unchanging like colors, shapes, quantities, space, time—the kinds of objects studied by Arithmetic and Geometry.Whenever I'm awake or sleeping 2 plus 3 is always equal to 5. Therefore, Simple things are the things that Rene Descartes can trust.

Composite and Simple Things

Summary of Meditation I. Of the things which may be brought within the sphere of the doubtful.