The main target of Descartes’ philosophical arguments is to prove a unique universal science which could be achieved merely through a thorough and rational method. It should be noticed that Descartes’ philosophy, which is based on rationalism, is at variance with the older traditions including those of the antiquity and middle Ages. That is so because Descarte’s main focus is modern sciences and his main attempt in the realm of First Philosophy is to prove the existence of a kind of reason that is not only well-equipped with method but also solely something to distinguish the sequence of things and comprehend the order of affairs. Moreover, First Philosophy has taken its final form as if by the dictates of the demands of this very method. This topic is discussed and analyzed in the present article considering different sciences and particular examples of this subject as presented by Descartes himself