Just as a person has been given the ability to infer through parables and induction, to make a whole through components and then explain the components through the whole, to assimilate ideologies through what is obvious and to draw analogies from what can be felt through the senses for what cannot be felt, he has also be given the ability to distinguish between good and evil and to make a distinction between what is right and what is wrong and in fact he even has a comprehension of his Lord and his justice. We have already alluded to these abilities of man earlier. Thus a prophet is not needed to inform people of these things. All these are ingrained in his nature and innately found in him. The Qur’ānic verse (4:163-165) which has been earlier referred to at the beginning of this section “Belief in the Prophets” shows that the need for a prophet did not arise to inform man of these things; it arose because of two other reasons:

Firstly, for completion of guidance. This means that man be reminded of whatever is ingrained in his nature in concise form and of whatever he has known eternally and all its details be specified for him. In certain verses, the Qur’ān has regarded this to be a completion of divine favour:

وَجَعَلْنَاهُمْ أَئِمَّةً يَهْدُوْنَ بِأَمْرِنَا وَأَوْحَيْنَا إِلَيْهِمْ فِعْلَ الْخَيْرَاتِ وَإِقَامَ الصَّلَاةِ وَإِيْتَآء الزَّكَاةِ وَكَانُوْا لَنَا عَابِدِيْنَ
And We made these [prophets] leaders to give guidance at Our behest, and revealed to them to do pious deeds, show diligence in the prayer and give zakāh. And they worshipped none but Ourself. (21:73)

Secondly, for itmām al-hujjah. This means to awaken man from his slumber of unawareness and after providing the testimony of his intellect and knowledge provide another testimony through these prophets to such an extent that no one is left with any excuse to deny the truth:

يَا مَعْشَرَ الْجِنِّ وَالإِنْسِ أَلَمْ يَأْتِكُمْ رُسُلٌ مِّنكُمْ يَقُصُّوْنَ عَلَيْكُمْ آيَاتِيْ وَيُنْذِرُوْنَكُمْ لِقَاء يَوْمِكُمْ هَـذَا قَالُواْ شَهِدْنَا عَلَى أَنْفُسِنَا وَغَرَّتْهُمُ الْحَيَاةُ الدُّنْيَا وَشَهِدُواْ عَلَى أَنفُسِهِمْ أَنَّهُمْ كَانُواْ كَافِرِيْنَ ذَلِكَ أَن لَّمْ يَكُنْ رَّبُّكَ مُهْلِكَ الْقُرَى بِظُلْمٍ وَأَهْلُهَا غَافِلُوْنَ
“O Jinn and men! Did there not come to you prophets from among you who proclaimed to you My revelations and warned you of [your] meeting with this day?” They will reply: “We bear witness against our own souls” – And indeed, the life of this world deceived them and they testified against themselves that they were disbelievers – this was because your Lord does not destroy cities because of their oppression if their inhabitants are not aware of the truth. (6:130-131)