Al-G̱ẖazālī's positive contribution to the Philosophy of his country, however, is found in his little book--Mis̱ẖkātal-Anwār--where he starts with the Quranic verse, "God is the light of heavens and earth", and instinctively returns to the Iranian idea, which was soon to find a vigorous expounder in Al-Is̱ẖrāqī. Light, he teaches in this book, is the only real existence; and there is no darkness greater than non-existence. But the essence of Light is manifestation: "it is attributed to manifestation which is a relation"[78:1]. The Universe was created out of darkness on which God sprinkled[79:1] his own light, and made its different parts more or less visible according as they received more or less light. As bodies differ from one another in being dark, obscure, illuminated or illuminating, so men are differentiated from one another. There are some who illuminate other human beings; and, for this reason, the Prophet is named "The Burning Lamp" in the Qur’ān. [78:1] Mis̱ẖkātal-Anwār, fol. 3a. [79:1] In support of this view Al-G̱ẖazālī quotes a tradition of the prophet. Mis̱ẖkātal-Anwār, fol. 10a. The physical eye sees only the external manifestation of the Absolute or Real Light. There is an internal eye in the heart of man which, unlike the physical eye, sees itself as other things, an eye which goes beyond the finite, and pierces the veil of manifestation. These thoughts are merely germs, which developed and fructified in Al-Is̱ẖrāqī's "Philosophy of Illumination"--Ḥikmatal-Is̱ẖrāq. Such is the As̱ẖ‘arite philosophy. One great theological result of this reaction was that it checked the growth of freethought which tended to dissolve the solidarity of the Church. We are, however, concerned more with the purely intellectual results of the As̱ẖ‘arite mode of thought, and these are mainly two:-- (1). It led to an independent criticism of Greek philosophy as we shall see presently. (2). In the beginning of the 10th century when the As̱ẖ‘arite had almost completely demolished the stronghold of Rationalism, we see a tendency towards what may be called Persian Positivism. Al-Birūnī[80:1] (d. 1048) and Ibn Haiṯẖam[80:2] (d. 1038) who anticipated modern empirical Psychology in recognising what is called reaction-time, gave up all inquiry concerning the nature of the supersensual, and maintained a prudent silence about religious matters. Such a state of things could have existed, but could not have been logically justified before Al-As̱ẖ‘arī.