I'm not totally sure that you have to get rid of one or the other, but Nihilism theories seem to have a lot less explanatory power than do dualistic ones to me. In this paper I will argue that the clearest difference between Descartes and Nietzsche here is that whereas Descartes thought that ideas are passive, Nietzsche thought the opposite. Well, Descartes tries to prove the existence of God, which is the condition of establishing/ensuring an external world, including inter-subjectivity, in his view. God is a precondition of the innate ideas and connection with the surrounding world. There's no doubt in the mind of Descartes that God exist. Hence, he is claiming that faith/religion is a pre-condition of any understanding. Moreover, according to Rene Descartes’ Discourse on Method and Meditations on First Philosophy states “I think, therefore I am”. Descartes believed that finding one indubitable truth, together with a means for employing it, will be the foundation of a true philosophical system. Descartes' argument was that whatever doubt I may have, I cannot doubt that I am doubting - that I exist as doubting and, in general, thinking, and even an evil genius cannot trick me into thinking that I am doubting. Descartes defined the human mind as existing because it can think, and distinguished that the mind and the body are separate entities. On the other hands, Nietzsche is trying to reduce religious phenomena to psychological. The belief in God and Christianity is an attempt to escape the contingency of life by adopting the norms of a larger group. It's an expression of a sheep or slave mentality, which Nietzsche opposes. He believes in the will of one man, a strong willed man who doesn't have to live by the dogma of his civilization (he criticizes also democracy and socialism - and I'm sure that he would be equally concerned with the consumerism of today). Furthermore, in Nietzsche opinion the idea of God has been refuted by history as a psychological illusion of the human mind - that's what he means when he states, that God is dead. Earlier, (for instance in ancient Greece) the mind of man weren't evolved to recognize the true nature of the phenomenon of God - and such a belief is natural and understandable. But the phenomenon of God has proven in time to be a still emptier concept - as man finds science able to provide answers, God is expendable. I couldn’t find a better answer than the Descartes’s one to answer to Nietzsche opinion of the idea of God. “In order to determine whether there is anything we can know with certainty.” Descartes says that we first have to doubt everything we know. Such a radical doubt might not seem reasonable, and Descartes certainly does not mean that we really should doubt everything. What he suggests, though, is that in order to see if there is some belief that cannot be doubted, we should temporarily pretend that everything we know is questionable. This pretense is what is called a hypothetical doubt. To make sure that we take the pretense seriously, Descartes suggests that there might be good arguments to think that such doubting is justified (and thus more than simply something we should pretend to do). His arguments fall into two categories: those aimed against our sense experiences and our supposition that we can distinguish between being awake and dreaming, and those aimed against our reasoning abilities themselves. All in all, in my paper I have argued that the interpretation of God and the existence in Nietzsche ideas is based on a misunderstanding. The interpretation overlooks an important aspect in Nietzsche’s philosophy, namely the fact that he equates truth with certainty and sees ideas as acts of understanding involving truth. Even though Nietzsche’s theory of ideas is drastically different from Descartes’s theory and in many respects is a reaction against Nietzsche’s theory, Descartes’s theory of existence is well worth examining in its own right, not always in the Cartesian light.