Man is a changeable creature, a complex structure containing his being, his nature, soul and intelligence. Every individual personality is similarly of a complex nature, in which there are causes of good and evil. On the one hand, man has been created with emotions and instincts, such as self-love, desire and pride; he obeys the call of his desires, has a natural disposition to show his superiority over others, to own things, and to take for himself that which belongs to others; he rushes recklessly at the objects and ornaments of this world. As Allah has said:

Lo! Man is in the way of loss. (103;2)and:

Surely man waxes insolent, for he thinks himself self-sufficient. (96; 6,7)

and also:

Surely the soul of man incites to evil. (12; 53)

There are other verses which clearly talk about and point to the desires and feelings of the human soul which was created with man.

On the other hand, Allah has given intelligence (aql) to man to guide him to what is in his interest and to the way of goodness, and He has also bestowed on him a conscience which prevents him form doing evil and oppressing others, and which also upbraids him when he has sinned.
There is continual enmity and struggle between man's desires and his intelligence. One whose intelligence overcomes his desires will attain the highest position among mankind and a perfect spirituality, but one whose desires to conquer his intelligence will be among the great losers, the lowest of mankind and comparable in nature to the beasts.

The desires and their legions are stronger than intelligence and its armies, and this is why most people go astray and wander far from the straight path of guidance, through obeying their desires and answering the call of their emotions. As is said in the Qur'an:

And though thou try much, most men will not believe. (12; 103)

Besides, men is reluctant and unaware of all the facts and secrets of the world around him, and since he is also ignorant of his own self, how can he know all that will make him prosperous and what will make him suffer; how can he know everything that is in his own interest or in the interests of mankind as a whole? Whenever he advances with a new discovery, he sees his own ignorance and realizes that he knows nothing. It is because of this that Man has an insistent need for someone to show him the clear, straight path to prosperity and to give support to his intelligence, so that it may overcome its unruly, persistent enemy, and so that he may prepare to fight his emotions.

Man is desperately in need of someone to help him to the path of goodness and happiness, especially when his emotions deceive him, disguising his bad actions as good and his good actions as bad, as a result of which his intellegence is confused and cannot find the right path to prosperity and distinguish between the real good and the real evil. Everyone of us has succumbed on tis battlefield, either consciously or unconsciously, except the man whom Allah protects. It is difficult for an enlightened, civilized man to attain the way of goodness and happiness, so how much more difficult is it for an ignorant, unschooled man!

When all people co-operate and consult with one another and deliberate together they are still unable to understand what is useful and what is harmful for themselves and for society. So Allah thorough His Grace and Mercy for mankind sends them a messenger. The Qur'an says:

He it is who sent among the unlettered ones a messenger of their own, to recite unto them His signs, and to purify them and to teach them the Book and Wisdom. (62;2)

and he (the messenger) warns them concerning what is evil and gives glad tidings to them about what is good for their welfare.

(The giving of) this Grace is necessary for Allah, because it is a sign of His perfection, and His is Kind and Generous to His servants. When a man deserves His Mercy and Grace, Allah must grant to it to him, because of "necessary for Allah" is not that anyone forces Him to act in this way and that it is necessary for Him to obey, but it means that this is an inseparable attribute of Allah, i.e. Mercy and Grace cannot be separated from Him, in the same way as we say that His Existence is inherent in Him, or that He is necessarily Existent, i.e, His Existence is co-existent (with Him) and cannot be separated (from Him).