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To attain the authority of any text including revealed or non revealed constitutes the first condition for the validity of the understanding anding of the addressee. This act depends on certain elements such as asurity for the subsistency of the text with out any change or alteration in its parts. There are three methods for abtaining the authority of the text of the Quran in the context of subsistence as follows: 1- refuting any change in the text, 2-preparing the change of the text, and 3-separating the parts of the text. The first method is the current method of two sects which is carried out through affirming the unchangebility of the Quran and negating the distortion of the Quran. The second method rulls out the possibility of the Quran through the infalliable imams who refer to the Quran. In the third method the authority of each part of the Quran separatety will be attained. The first and the second methods have an old background. The third method was put forward in the 11th century (A.H) and then was expanded in recent century by the scholars of Ilm al-usul. To attain the authority of the text of the Quran is possible only through refuting the possibility of the alteration of the text and two other methods fact serious challenges.