 ٤ـ وَعَنْهُ عَنْ أَحْمَدَ بْنِ إِسْحَاقَ قَالَ كَتَبْتُ إِلَى أَبِي الْحَسَنِ الثَّالِثِ (عَلَيْهِ السَّلام) أَسْأَلُهُ عَنِ الرُّؤْيَةِ وَمَا اخْتَلَفَ فِيهِ النَّاسُ فَكَتَبَ لا تَجُوزُ الرُّؤْيَةُ مَا لَمْ يَكُنْ بَيْنَ الرَّائِي وَالْمَرْئِيِّ هَوَاءٌ لَمْ يَنْفُذْهُ الْبَصَرُ فَإِذَا انْقَطَعَ الْهَوَاءُ عَنِ الرَّائِي وَالْمَرْئِيِّ لَمْ تَصِحَّ الرُّؤْيَةُ وَكَانَ فِي ذَلِكَ الاشْتِبَاهُ لانَّ الرَّائِيَ مَتَى سَاوَى الْمَرْئِيَّ فِي السَّبَبِ الْمُوجِبِ بَيْنَهُمَا فِي الرُّؤْيَةِ وَجَبَ الاشْتِبَاهُ وَكَانَ ذَلِكَ التَّشْبِيهُ لانَّ الاسْبَابَ لا بُدَّ مِنِ اتِّصَالِهَا بِالْمُسَبَّبَاتِ.
 4. It is narrated from the same narrator (Ahmad ibn Idris) from Ahmad ibn Ishaq who has said the following. “I wrote to Imam abul Hassan the 3rd and asked him about eye-witnessing Allah’s self and the differences among people about this issue. The Imam  answered in writing.” “Eye-witnessing Allah’s self is not possible until there is air (light-carrier medium) that would let the light reach the eye. If air is remove from (space between) the viewer and the object, no eye-witnessing will take place. In this is ground for similarity. When the viewer and the object in view would have the same medium that make eye-witnessing possible a similarity must exist therein. (When applying this to the case of Allah) it is an analogy and similarity. The means must have a connection with the source.”