Rene Descartes' arguments in "Meditations on First Philosophy" are questionable to exactly how valid and sound they really are. His proof for the existence of God in the fifth meditation is an example of one of his invalid and therefore unsound arguments. Throughout the meditations Descartes refers to clear and distinct ideas. Descartes first introduces doubt to the reader by saying that one cannot trust these clear and distinct ideas. "I have noticed that the senses are sometimes deceptive; as it is a mark of prudence never to place our complete trust in those that have deceived us even once." (Descartes, 60) He introduces doubt through the senses, dreams, and through the possibility of an evil genius at work. For instance he states that "There is no sure sign that I can tell that I am awake.

If there are no sure signs that I can tell that I am awake then there is reason to doubt I am awake. Therefore there is reason to doubt I am awake." (Descartes 60) This is how Descartes shows that we may be dreaming even though during these dreams we can experience authentic truths. He also he goes on to state that, "If there is reason to doubt that I am awake then there is reason to doubt that I am sitting by the fire. So then there is reason to doubt that I am sitting by a fire even though I see and feel a fire." (Descartes 60) This Descartes believes could be true because there may be an evil genius at work, whose sole purpose is to put his entire effort into deceiving us.

Descartes believes that there may be the presence of this evil genius because he knows that he is an imperfect being and rationalizes that if there was a God that he would be perfect and therefore make only perfect things, so clear and distinct ideas cannot be fully trusted due to the fact that a powerful and clever evil genius may be at work. Descartes then uses clear and distinct ideas in order to justify scholastic metaphysics. Scholastic Metaphysics deals primarily with reality. There are two kinds of reality, formal which everything must possess and objective. There are also three levels of these realities; God, substance, and attributes. The level of reality that something possesses is based on its ontological independence.

God is completely ontologically independent therefore he needs nothing in order to exist and has the highest level of reality. Substance such as mind and body need God in order to exist, therefore have lesser levels of reality. Attributes such as shape or extension need either a mind or body to exist in. These substances such as mind or body are then in turn dependent upon God which would then make an attribute possess the lowest level of reality. In order to determine the level of reality that something possesses Descartes turns to using clear and distinct ideas. The methodology for discovering the level of reality is based on four questions.

What level of reality does it possess formally or as the thing itself? Does it represent something? If yes, what does it represent? If the represented did exist, what level of formal reality would it possess? This deals with the objective reality for a scholastic, but for Descartes objective reality deals with the representational content of an idea. So it only deals with these ideas and so ideas will represent things. The problem is that Descartes does not trust his clear and distinct ideas so whatever ideas he acquires from Metaphysics cannot be completely trusted because he has previously rejected them. During meditation five Descartes attempts to prove the existence of God. He uses an example of a triangle to demonstrate the idea of essence. A triangle cannot be thought of with out having three sides, angles that add up to one hundred and eighty degrees, and so on.

These ideas are the essence of the triangle and if taken away will no longer make the object a triangle. Descartes explains that he cannot think of God without thinking of him as existing, like one cannot think of a triangle without having three sides and angles adding up to two right angles. This shows that existence is a predicate to God, it is always thought of in conjunction with the idea of God. Descartes states from Scholastic Metaphysics, that God needs nothing, is supremely perfect, and ontologically independent because he is the highest level of reality and needs nothing for existence.

God must possess all perfections since he needs nothing. Existence is a perfection. So therefore God must exist. Descartes then uses his proof of God in order to prove the validity of clear and distinct ideas.

He goes on to say that, "Once I perceive that there is a God, and also understood that everything else depends on him, and that he is not a deceiver (evil genius), I then conclude that everything that I clearly and distinctly perceive is necessarily true." This proof of clear and distinct ideas is suppose to show that in the beginning you can use these clear and distinct ideas as a valid starting point for the entire argument. The entire proof of God that Descartes provides at first seems to work and also be logical. Upon closer inspection of this proof though we see that Descartes makes an assumption in the very beginning that clear and distinct ideas are true in order to gain Scholastic Metaphysics and ultimately prove the existence of God. This assumption about whether clear and distinct ideas are true and that they can be trusted is later then justified by his proof of God. The assumption that he makes about clear and distinct ideas creates a circular argument. His whole argument is never based on a truth to start with only an assumption.

This makes the argument invalid and also therefore unsound.