Allah, the Wise, has said:
وَ مَا عِنْدَ اللهِ خَيْرٌ وَ أََبْقىَ أَ فَلاَ تَعقِلُونَ
"And whatever is with Allah is better and more lasting; do you not then understand." 
Imam Sadiq (a.s) said:
لاَ بَلَغَ جَـمِيعُ الْعَابِدِينَ فِي فَضْلِ عِبَادَتِهِمْ ماَ بَلَغَ الْعَاقِلُ.
"All the worshippers, despite the excellence of their worship, do not achieve what a person with intellect achieves." 
O' Lord! What have you not granted those, to whom You have granted intellect, and what have you granted those, to whom You have not granted intellect! 
The personality of a person is founded upon his intellect and one who does not seek the assistance of this faculty in his affairs shall suffer loss and harm.
Intellect is one of the Divine soldiers, and an internal argument and proof. Intellect, irrespective of whether it is inherently possessed or empirically achieved, brings about progress and advancement of man.
The Prophets used to guide the people by speaking to them in accordance with their intellectual capabilities, and on the Day of Judgment, Allah shall reckon the deeds of his servants according to the measure of their understanding and intellect. Blind-following brings about eternal damnation in the hereafter - as was the case with Bani Israel who, in a fit of fanaticism and foolishness, killed 70 Divine Prophets in one day!
1 – Slaughtering the Gourd
After Muawiyah had embarked upon his policy of opposition towards the Commander of the Faithful(a.s), he once resolved to test the measure of obedience of the people of Syria towards him and so consulted 'Amr 'as in this regard.
Amr As said: "Command the people to slaughter the gourd before eating it just as they slaughter a sheep. If they act in accordance with your order then they are your allies, but if not, then they are not yet fully obedient to you."
Muawiyah ordered that henceforth the people should slaughter the gourds just as they slaughtered the ship; the people too, without the slightest of objections, acted in compliance and subsequently this innovation became a customary practice throughout Syria.
It was not long before the news of this innovation reached the ears of the people of Iraq prompting some of them to question the Commander of the Faithful(a.s) about it whereupon the Imam (a.s) replied:
اَلقَرعُ لَيسَ يُذَكَّى فَكُلُوه
"It is not required to slaughter a gourd in order to eat it. Be wary, lest the Satan takes away your intellect and satanic ideas leave you confused and lead you astray."
2 – Mature In Intellect
With the intention of suppressing a group of rebellious enemies existing around Mecca and Madinah, the Noble Prophet (s.a.w) readied a rapid-strike commando unit for the purpose of advancing secretly upon the enemies in the darkness of the night and overcoming them and appointed a youth from the tribe of Hudhail as the commander of this unit. A shallow-minded person remonstrated saying: "Why have you appointed a youth as our chief? We refuse to obey his orders. You ought to have appointed an elderly person as the chief and commander (of the army)."
The Noble Prophet (s.a.w) said: "O' Shallow-minded person! Although he is a youth, nevertheless he possesses a strong heart and a sound intellect, whereas the elders that you talk about, although they possess white beards and apparently should be given the leadership, however, their hearts are dark as pitch.
On numerous occasions I have put this youth to test and found him to be mature in intellect. Elderly in age (but) lacking in intellect yields no benefit. Strive, to the maximum extent possible, to be elderly in intellect and religion, for leadership is determined not by age but by intelligence, reflection and a pure luminous heart."
3 – The Consequence of Foolishness
In the biography of Hajjaj Ibn Yusuf Thaqafi - the bloodthirsty Umayyad, it has been reported that his mother, Fari'ah, had initially been the wife of Harith Ibn Kaldah - a well-known doctor, who divorced her when she picked her teeth at an inopportune time; it was later that she entered into the wedlock of Yusuf Ibn 'Aqil Thaqafi.
Hajjaj, at the time of his birth, did not possess an excretory opening; left with no other option, his parents were forced to create an opening in his rear.
In addition to this, he would also not drink the milk from the breast of his mother and this left the parents worried and wondering as to what should be done.
One day, an evil person approached them and instructed them that in order to remedy this problem they should kill a black goat and make Hajjaj drink its blood. When the goat was killed and the blood put into his mouth, Hajjaj began sucking and licking it. The following day the person directed them to kill a goat and pour its blood into his mouth. On the third day he ordered them to kill a black snake, pour its blood into his mouth and rub it upon his face as well whereupon from the fourth day onwards Hajjaj began feeding himself with the milk of his mother.
As a result of this ignorant act, he grew up into such a savage and bloodthirsty individual that he would say: "I derive maximum pleasure by shedding blood - especially the blood of the descendents of the Noble Prophet (s.a.w)."
He was appointed governor and the commander of the army by 'Abdul Malik Ibn Marwan and ruled for twenty years till he died in the year 95 ah (during the rule of Walid Ibn 'Abdul Malik) at the age of fifty four.
In the course of this period he killed a hundred and twenty thousand people, and at the time of his death, his roofless prison contained fifty thousand male and thirty thousand female prisoners - majority of them bare and unclothed.
Amongst those killed by this cruel tyrant were Kumail Ibn Ziyad Nakha'i - the companion of Ali (a.s), Qambar - the slave of Ali (a.s), Yahya Ibn Umm al-Tawil - a companion of Imam Sajjad (a.s), Sa'id Ibn Jubair, who has been greatly praised and commended by Imam Sajjad (a.s) and numerous other celebrated personalities.
4 – Ali and the Astrologer
There are some who are heedless with respect to reflection, reasoning and tawakkul, and instead, turn to soothsayers and astrologers, who have cleverly started their business in order to swindle the people of their money. As an example, we shall present an incident that transpired during the time of Imam Ali (a.s). The Commander of the Faithful(a.s) and his army had started out for the battle of Nahrawan against the Kharjites, and having reached the city of Madain, they pitched their tents. The next morning, as they were about to commence their journey, an astrologer approached them and said: "My astrological calculations reveal that it is not in your interest to advance in this hour. Commence your journey after three hours and you shall be victorious."
Hearing this, the Imam (a.s) said: "Whoever upholds your words has rejected the Qur`an of Allah."
He (a.s) then asked: "Do you possess knowledge as to which family has taken over the reins of leadership in China?"
The astrologer replied: "I have no knowledge."
The Imam (a.s) questioned: "What is that star, which when rises, stirs up lust within the camels?"
The astrologer confessed: "I have no idea."
The Imam (a.s) asked: "The rise of which star stirs up passion within the cats?"
He said: "I do not know!"
He (a.s) asked: "Inform me of the thing that is concealed beneath the hoofs of my horse."
When the astrologer had once again pleaded ignorance, the Imam (a.s) said to him: "Within the earth, below the feet of my horse, lies a jar filled with gold coins and beneath which a serpent lies asleep."
When the place was dug up, the people witnessed that the scenario was exactly as it had been described by the Imam (a.s).
Observing this, the astrologer was totally bewildered; the Imam (a.s) took possession of his books, ordered them to be destroyed and then said to him: "The next time you try to attract the people towards yourself by means of astrology, I shall put you behind bars."
5 – The Insanity-Exhibiting Wise Person
Every thing is recognized by means of its attributes and effects; sagaciousness and intelligence of a person become manifest by means of his words and deeds.
Behlool (d. 190 ah), despite the fact that his father was the uncle of Haroon al-Rashid, exhibited himself as a lunatic in order to abstain himself from accepting the post of judge and issuing the death sentence for the seventh Imam (a.s).
One of the most evident examples of his ration and intellect was the incident of his entry into the class of Abu Hanifah - one of the Sunnite leaders.
Once, as he happened to pass by the class Abu Hanifah, he heard him say: "Jafar Ibn Muhammad (a.s) has said to his students three things, which I do not approve of.
He (a.s) has said: "Satan shall be chastised in the fire of Hell." But how can he be punished by means of fire when he has himself been created out of fire?
He (a.s) also says: "Allah cannot be seen", whereas every entity can be perceived by means of vision.
He (a.s) also says: "Man, in performing his actions, is free and has a choice", whereas, in reality, Allah is the Creator and His servants have no discretion and freedom.
Having heard this from Abu Hanifah, Behlool picked up a clod of earth and hit him on the head, injuring him and prompting lamentations from him.
His students rushed towards Behlool and seizing him, presented him before the caliph.
Abu Hanifah said to the caliph: "Behlool has struck me with a clod of earth and injured me."
Behlool retorted: "If he speaks the truth ask him to show the pain."
Then turning to Abu Hanifah, he said: "Have you not been created from earth? How then can earth harm and injure you? (Besides) What wrong have I done? Are you yourself not of the opinion that it is Allah, who performs all the acts and deeds, and man has no discretion and freedom? Thus, you should register a complaint against Allah and not against me."
Abu Hanifah, having received the answers to his objections, withdrew his complaint and went his way."
 Suratul Qasas (28), Verse 60
 Jami~ al-Sa~adat, vol. 1, pg. 111
 Khwajah ~Abdullah Ansari
 Dastan-ha Wa Pand-ha, vol. 1, pg. 92; al-Kafi, vol. 6, pg. 370
 Historical accounts have reported many such appointments on the part of the Holy Prophet - amongst them being the appointment of I~tab Ibn Asid, a 21 year old youth, as the ruler of Mecca and the appointment of the youth Usama b. Zaid as the commander of his army.
 Dastan-ha-e-Mathnawi, vol. 3, pg. 64
 Tatimmah al-Muntaha, pg. 66
 Of course, the issue of the auliya of Allah and those, who have strived towards spiritual purification, differ vastly from the others, for their words are light (nur) and if, at times, they were to say something to someone, it would surely occur and hence such personalities should not be compared to the others.
 Surat Luqman (31), Verse 34: إِنَّ اللٌّهَ عِنْدَهُ عِلْمُ السَّاعَةِ وَ يُنَزِّلُ الْغَيْثَ وَ يَعلَمُ ماَ فِي الأََرحَامِ
 Jame~ al-Nurain, pg. 15; Bihar al-Anwar
 Shagirdan-e-Maktab-e-Aimmah, pg. 262; Qamus al-Rijal, vol. 2, pg. 252