The progress of science and literature in Khorasan and Transoxiana stopped from the extinction of the Sassanids until the rise of Iranian governments. During the era of Tahirids and Saffarids, Persian language and literature found new life and firm and reliable steps were taken towards cultural and scientific progress. The Saffarids were the first native families of Khorasan who replaced the Persian language with the Arabic language. With the establishment of sovereignty in Khorasan, the intellectual and philosophical movement of the thinkers and scholars of this region was resumed and the temporary cultural stagnation ended. Scientific developments caused some to call the fourth century "The Islamic Renaissance". The period under discussion (3rd, 4th and 5th centuries A.H.) is considered one of the most important Persian cultural periods, and it is necessary to examine the factors of growth and decline of thought and its relationship with sovereignty. By explaining the behavior of Samanid and Ghaznavid kings towards intellectuals, the quality of scientific schools and the importance of local families become more clear.
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