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For searehing about tntthful proof we are in need of two ways, historical research, that is which philosopher payed attention to this proof for the first time, and then who and how they continued and
developed it. And through thinking about form and substance of proof find out the bases of the proof, what kind of analogy had been used and
how they end to the elemen tnalls. This article tries to consider these two important points, and shows the formation of trathful prooffrom the age of Farabi until the contemporary.