One of the most notable architectural aphorisms in modern period must be undeniably Louis Sullivan's, 'Form Follows Function.' The aphorism has been not only an important source of new aesthetic but also an formal principle of machine age. Other most famous source in order to justify modern aesthetic was the short essay by an cynical critic, Adolf Loos(1870-1933), 'Ornament and Crime' of 1908. Apart from what the essay asserted it is also famous for the influence of Sullivan's architectural notion during Loos' States staying. For Architectural historians of the early 20th century this connection is so useful to create a legacy of modern architecture. The historians seemed to believe that Loos understanded Sullivan's aphorism on which the historians wanted to focused. When we however look into two buildings designed and built in the period of publishing both aphorism and essay there must be a big fissure between the buildings and the historians interpretations. With this view point this study aims at showing the true meanings of Sullivan's aphorism and Loos' essay and also the big difference between the machine age's aesthetic and theirs.

Since he was a leading figure in nineteenth century architecture, Viollet-le-Duc's architectural theory is crucial to the foundation of modern architecture. He has been called a Gothic Revivalist, a Structural Rationalist and a Positivist. The first title was perhaps due to his vigorous restoration of Gothic works such as $N\hat{o}tre$ Dame, but he did not adore the Gothic style just for itself. Rather, he hoped to deduce some principles from the style. So how did he manage this? In his book "Entretiens sur l'Architecture (Lectures on Architecture), published between 1864 and 1872, he mentions using Descartes' four rules for reaching architectural certainty in contrast with the chaotic situation during that modernising period. Furthermore Viollet-le-Duc's theory can be seen as a serious attempt to translates Descartes' philosophical rules into systems of architectural speculation. Descartes' four rules of doubt are anchored in mathematical propositions, and without mathematical distinctions, none of these rules are valid. In other word, mathematics for Viollet is the yardstick of judgement between distinctness and indistinctness. Many architectural problems arise from this view. In this paper, the validities of applying Descartes' method of doubt to architectural discourse will be discussed in order to address the question:-Did Viollet-le-Duc clearly grasp Cartesian method by which memory was erased from the world?