It was related from Muhammad ibn 'Abdallah al-Khurasani, the servant of Imam Reza (A.S.) that a man from among the unbelievers (zanadiqah) entered the presence of the Imam Reza (A.S.) with whom was a group of people, Abu-l-hasan (the Imam) said to him.
"Dost thou see that if the correct view is your view-- and it is not your view - then are we not equal? All that we have prayed, fasted, given of the alms and declared of our convictions will not harm us."
The unbeliever remained silent. Then Abul HasanA.S), said, "If the correct view is our view - and it is our view - then have not you perished and we gained salvation?"
He said, "God's mercy be upon thee. Then let me know, how is He and where is He?"
Abu-l-Hassan(A.S) answered "Woe upon thee, surely the opinion thou hast adopted is mistaken. He determined the 'where', and He was, when there was no where; and He fashioned the 'how' and He was, when there was no 'how'. So He is not known through 'howness' or 'whereness' or through any form of sense perception, nor can He be gauged by anything."
The man said, "So then surely He is nothing (la shay) if He cannot be perceived by any of the senses."
Abu-l-Hasan(A.S) said, "Woe upon thee! When thy senses fail to perceive Him, thou deniest His lordship. But when our senses fail to perceive Him, We know for certain that He is our Lord and that He is something different from other things (shay' di-khilaf al-ashya)."
The man said, "Then tell me, when was He?"
Abu-l-Hasan(A.S) said, "Tell when He was not, and then I will tell you when He was."
The man said, "Then what is the proof of Him?"
Abu-l-Hasan(A.S), said, "Surely when I contemplate my body and it is impossible for me to increase or decrease its breadth and height, or to keep unpleasant things away from it or draw benefits to it, then I know that this structure has a maker and I acknowledge (iqrar) Him -- even though that which I had seen of the rotation of the celestial sphere through His power; the producing of clouds, the turning about of the winds; the procession of the sun, the moon and the stars; and others of His wondrous and perfectly created signs (ayat), had (already) made me know that (all) this has a Determiner (muqaddir) and Producer (munshi)."
The man said, "Then why has He veiled Himself (from men)?"
Abu-l-Hasan(A.S.) replied, "Surely the veil is upon creatures because of the abundance of their sins. As for Him, no secret is hidden from Him during the day or the night."
The man said, "Then why does the sense of sight perceive Him not?"
Abu-l-Hasan(A.S.) answered. "Because of the difference between Him and His creatures, who are perceived by the vision ot the eyes, whether their own or others. Then He is greater than that sight should perceive Him, imagination encompass Him, or the power of reason delineate Him."
The man said, "Then define His limits (hadd) for me."
He answered, "He has no limits."
The man asked, "Why?"
He answered, "Because every limited thing (mahdud) ends at a limit. If limitation (tahdid) is possible, then increase is possible. If increase is possible, then decrease is possible. So He is unlimited. He neither increases nor decreases. Nor is He capable of being divided or imagined."
The man said, "Then tell me about your saying that He is Subtle, Hearing, Seeing, Knowing and Wise. Can He be the Hearing without ears, the Seeing without eyes, the Subtle without working with the hands and the Wise without workmanship (sanah)?"
Abu-l-Hasan(A.S.), said, "Surely a person among us is subtle in accordance with (his) skill in wokmanship. Hast thou not seen the man who undertakes a task and is subtle in his handling of it, so that it is said, 'How subtle is so and so!' Then how should it not be said of the Majestic Creator that He is Subtle, when He creates a subtle and majestic creation, places in its living creatures their souls, creates every kind different in from its own kind, and none resembles another? Each possesses in the composition of its form a subtlety from the Subtle and Aware Creator.
"Then we looked upon the trees and their bearing of delicate things, whether edible of inedible, and we said at that, 'Surely our Creator is Subtle, (but) not like the subtlety of His creatures in their workmanship. 'And we said, 'Surely He is Hearing for not hidden from Him are the sounds of His creatures between the Throne and the earth, from a mote to what is larger than it, and in the land and the sea. And their words are not confused by Him.' At that we said, 'Surely He is Hearing, but not through ears.'
"Then we said, 'Surely He is Seeing, but not through eyes, for He sees the trace of a black speck on a dark night on a balck stone. He sees the tracks of an ant on a pitch-black night. He sees what is harmful for it and what beneficial, and the result of its cohabitation, and its young and descendents. 'And at that we said, 'Surely He is Seeing, but not like the sight of His creatures'."
The man did not leave until he had embraced Islam. The Imam(A.S.), said other things as well.