SOCRATES,  Plato and Aristotle - the Trinity of the teachers of the West - laid the philosophic foundations of its culture and later contributed to Islamic scholasticism.
Hadn't God said in the Q'uran that He is the Light of the Heavens and of the Earth?
How well does the mystic poet, Jalaluddin Rumi, express his final release from the duality of self? "My place is the placeless, my trace is the traceless. It is neither body nor soul, for I belong to the soul of the beloved. I have put duality away and I have seen that the two worlds are one. One I seek, one I know, one I see, and one I  call."
who, in Sufi experience, grasped the certification of the Prophetic message in its essentials?
Tahfatal - Falasifah" to my mind ended as a squib, with a whimper. The angle of approach differed but not the approach.
His main contribution was not to push back philosophy (and with at Avicenna) into oblivion which he did not intend and if did, did not, succeed in. His main contribution in the service of Islam was to literally rout the Mutazallite School. And "it was probably to the good of Islam that Muatazallite rationalism, having done its work but not knowing where to stop, was defeated. Had it been successful, it is doubted whether the popular movements'out of which the regeneration of Islam was to come, could possibly have been tolerated, much less accommodated, within the frame-work of orthodoxy. Sooner or later the unity of Islamic culture would have suffered violent disruption" 
He did not invent Sufism, nor was he amongst the pioneers. It is as old as history. In the historical context of "Islam.”  I have called Abraham the first  Sufi, who gave up all - hearth, home, kith and kin, country to seek and follow the guidance. Ghazali, following him, gave up his eminent position, his prestigious status, his intellectual pursuits, his family, children, the Royal Court and deliberately turned his face against all worldly temptations and embarked on the new quest of inner peace and salvation and in the process made It attainable by all those who seek and knock at the door. But here too his rationalism did not desert him and he advised those who were inclined to follow the path that they should first "follow the path of scientific study and to acquire by laborious learning as much of the demonstrative sciences as human power can compass... And after that there is no harm in his electing to withdraw from the world and to devote himself entirely to God in an expectant mood." He gives a very explicit warning that "if the soul has not been exercised in the sciences that deal with fact and demonstration, it will acquire mental phantoms that it will suppose to be the truths descending Upon him." According to him "many a Sufi has continued for years in one such fancy before escaping from it, whereas if he had had a sound scientific education he would have been delivered out of it at once.”