With the Arab conquest of Persia, a new era begins in the history of Persian thought. But the warlike sons of sandy Arabia whose swords terminated, at Nahawand, the political independence of this ancient people, could hardly touch the intellectual freedom of the converted Zoroastrian.
The political revolution brought about by the Arab conquest marks the beginning of interaction between the Aryan and the Semitic, and we find that the Persian, though he lets the surface of his life become largely semitised, quietly converts Islam to his own Aryan habits of thought. In the West the sober Hellenic intellect interpreted another Semitic religion - Christianity; and the results of interpretation in both cases are strikingly similar. In each case the aim of the interpreting intellect is to soften the extreme rigidity of an absolute law imposed on the individual from without; in one word it is an endeavour to internalise the external. This process of transformation began with the study of Greek thought which, though combined with other causes, hindered the growth of native speculation, yet marked a transition from the purely objective attitude of Pre-Islamic Persian Philosophy to the subjective attitude of later