The 18th century French philosopher La Mettrie wrote L'homme-machine (1748) from a thoroughly materialistic point of view. He argued that the human being&sbquo both mind and body&sbquo is a machine&sbquo and offered the view that the content of the natural and medical sciences of the day&sbquo and even mental phenomena&sbquo were reducible to mechanical physical phenomena. Since&sbquo however&sbquo the level of knowledge concerning physiology of the brain was primitive at the time&sbquo and "machines" meant "clocks and mechanical dolls&sbquo" his interpretation of human mental phenomena was only mechanistic&sbquo abstract and high-flown&sbquo and was far from scientific. This theory&sbquo however&sbquo made a great impact on society since the view of humanity at the time was firmly based in Christianity. The concept of viewing the human being as a kind of machine can be traced back to the ancient Greek philosopher Epicurus. Moreover&sbquo the mind-body problem raised by Descartes has been carried to date as the central problem in the theory of human machine. Descartes defined the human body as an elaborate automaton&sbquo advocated the dualistic view that "the human being is composed of mind and body&sbquo" and specified a certain organ in the brain (conarium) as the locus of mind-body interaction&sbquo which has been disproved by modern medical science. In the 20th century&sbquo however&sbquo drastic progress in such fields as molecular biology and brain physiology clarified many human functions&sbquo particularly the physical foundations of mental phenomena. In the mid 20th century Norbert Wiener advocated the Cybernetics theory and defined the human being as a kind of finite automaton. The human machine theory gained a degree of concreteness from this and has settled in to date. It is a fact that the human machine theory is about to achieve a great success in modern science by reducing mental activities to physical phenomena. Criticism&sbquo however&sbquo that this theory contains conceptual confusion is still strong. It is difficult to argue against the claim that the human being is not a machine as it possesses free will. In design&sbquo this issue of whether the human being is machine or not is related to the definition of the relationship of man and machine&sbquo and human centered design.