Generally speaking&sbquo dualism was derived from a type of religious pluralism. It is a religious conceptual theory that is used to contrast and verify two polarized elements when examining their substantiality. The word was originally used by British oriental scholar Thomas Hyde in his Historia religionis veterum Persarum (1700) when he argued virtue and vice as relative principles and eternally conflicting religious systems. Thereafter&sbquo the word&sbquo as a religious term&sbquo was used by Pierre Bayle in a chapter on Zoroastrianism in his book Dictionnaire historique et critique (1702) and then by Leibniz in Theodicee (1710). Wolff is the one who turned this into a philosophical term. Dualism as a philosophical concept&sbquo however&sbquo dates back to Plato. The world of idea (intellect) and sensibility (phenomenon) is dualism. The concept journeyed from Aristotle to Descartes' spirit and material (body) and then to Kant's spirit (subjectivity) and material (objectivity). Dualism explains a process of change through a dualistic conflict&sbquo but in order to clarify the root of the conflict&sbquo it is inevitable&sbquo in the process&sbquo to call in the concept of monism. Monism&sbquo in essence&sbquo has a tendency to deny practical transformation to dualism regarding those conflicting elements. In design methods&sbquo dualism is effective as a basic and standard logic construction process particularly in the concept building stage. Therefore&sbquo in design&sbquo I would like to propose that dualistic matters should be treated as religious and philosophical design knowledge. When it is impossible to convey the advantages and effects of a design through a pluralistic design valuation&sbquo a dualistic logical strategy might be extremely effective.