Why Do We Need Religion?
Question

Why do people need religion? Isn’t it enough to have (man-made) laws that will regulate people’s lives?
Praise be to Allah.Why do we need religion?
Man’s need for religion is greater than his need for any of the other necessities of life, because man needs to know what pleases Allah and what angers Him; he needs to act in his own interests and to ward off things that will harm him. 
Shari`ah is what distinguishes between actions that will bring benefit and actions that will cause harm. This is Allah’s justice towards His creation, and His light which shines for His slaves. People cannot live without laws (Shari`ah ) to help them distinguish between what they should and should not do. 
Because man has a will, he has to know what he wants, is it beneficial or harmful? Is it good for him or bad for him?  
Some of these things may be known instinctively, some of it may be known by working it out in a rational manner, and some of it may only be known from the teachings and guidance of the messengers. (See al-Tadmuriyyah by Shaykh al-Islam Ibn Taymiyah, p. 213, 214; Miftah Dar al-Sa’adah, vol. 2, p. 383) 
No matter how impressive and attractive the atheist, materialist schools of thought may be, and no matter how many ideas and theories there may be, individuals and societies can never do without the true religion , they can never answer the needs of body and soul. The further the individual sinks into those ways, the more certain it becomes that he cannot find security or quench his thirst, and that there is no way out except through the true religion .
Ernest Renan says: 
“It is possible that everything we love could disappear and that rational thinking, science and industry could cease to exist, but it is impossible that religion could be eliminated. Rather it will remain as proof that materialistic thought which wants to restrict man to the narrow path of the base life of this world is false.” (See al-Din by ‘Abd-Allah Darraz, p. 87) 
Muhammad Farid Wajdi says: 
“It is impossible that the idea of religion could diminish, because it is the most refined inclination of the soul and its noblest emotion, in addition to being the inclination that ennobles man. Rather this inclination will increase and the religious nature of man will remain so long as he retains that reason which enables him to distinguish between beauty and ugliness. This instinct will increase according to his level of rationality.” (Al-Din by ‘Abd-Allah Darraz, p. 87)  
If man is far away from his Lord, then according to his level of knowledge and understanding he will realize the extent of his ignorance of his Lord and His attributes, and his ignorance of his own self and what is good for him or bad for him, what leads to bliss and what leads to doom, and his ignorance of such basic matters as astronomy, mathematics and the like.  At this point the wise man will move from the state of arrogance and pride to humility and submission, and will realize that behind all this knowledge is the All-Knowing, All-Wise, and that behind nature there is an Almighty Creator. This truth compels the objective seeker to believe in the unseen and acknowledge the true religion, and to respond to the call of human nature and innate instinct. If a person fails to do that he is going against his innate nature and sinking to the level of the dumb animals.  
Thus we may conclude that following the true religion – that which is based on belief in Allah Alone (Tawhid) and worshipping Him in the way that He has prescribed – is an essential element of life if man is to be a true slave to the Lord of the Worlds, and to attain happiness and be free of tiredness and exhaustion in this world and in the Hereafter. It is essential in order to perfect man’s rational thinking. In this way alone can reason fulfil its desires; without it man cannot fulfil his higher ambitions. 
It is an essential element for purifying the soul and disciplining the emotions, for in religion the noble emotions find fertile ground and an inexhaustible spring to help them achieve their goals. 
It is an essential element for strengthening willpower and supplying it with the greatest motives and power to resist the factor of helplessness and despair. 
How to attain full knowledge
On this basis, if there is anyone who says that man is sociable in nature, we must say that man is religious by nature. (See al-Din by ‘Abd-Allah Darraz, 84, 98), because man has two strengths, knowledge and willpower, and his ultimate happiness depends on him acquiring both. Full knowledge can only be attained by knowing the following: 

Knowing Allah, the Creator and Provider Who created man from nothing and bestowed blessings upon him.
Knowing the names and attributes of Allah, and the effect of these names upon His slaves.
Knowing the way to reach Him.
Knowing the obstacles that prevent man from knowing this way and the great blessings to which it leads.
Knowing yourself in a true sense, and knowing what your soul needs, what is good for it and what is bad for it, and knowing its faults and shortcomings.

These five matters will complete a person’s knowledge. 
Achieving perfect will power can only be achieved by paying attention to the rights of Allah over His slaves and fulfilling them sincerely, adhering to that and bearing witness to the blessings of Allah. These two strengths can only be perfected with the help of Allah, so man needs Allah to guide him to the Straight Path to which He guides His close friends. (See al-Fawaid, p, 18-19) 
Religion is a protective shield for society
Once we know that the true religion is the divine support that directs the potentials of man, then we know that religion is also a protective shield for society, because human life can only be strong when there is cooperation among the members of society. 
This cooperation can only be achieved by means of a system that regulates the relationships between them, defines their duties and protects their rights. 
This system needs a deterrent that will deter one from transgressing and encourage one to follow the system, one that carries weight in people’s hearts and prevents them from overstepping its limits. 
What is this authority? I say that there is no power on earth that can match the power of religion in protecting the sanctity of the system, guaranteeing the coherence of society and the stability of its system, and providing the means of peace and security. 
The reason for that is that man differs from all other living beings in that his voluntary actions and dealings are governed by something that can be neither seen nor heard, namely the religious belief that disciplines the heart and guides his faculties. Man is inevitably led by his belief, whether it is sound or corrupt. If his belief is sound, everything else will also be sound, but if it is corrupt then everything else will also be corrupt. 
Belief and faith regulate man
Belief and faith are the two things that regulate man and – as we can see in most cases – they are of two types: 

Belief in the importance of virtue and human dignity, and other abstract values which make noble souls feel ashamed to go against their principles even if they are spared the consequences of physical punishment.
Belief in Allah and that He is always watching and knows what is in our hearts, and that He knows secrets and that which is more hidden. The authority of SharI`ah is based on its commands and prohibitions, and makes a person feel shy before Allah, either out of love for Him, or out of fear of Him, or both. Undoubtedly this type of faith is the stronger of the two and carries more weight in human hearts. It is more able to resist the storms of desire and the upheavals of emotion, and it has more effect on the hearts of the masses and the elite.

For this reason, religion is the best guarantee for ensuring that people will deal with one another on a basis of fairness and justice, and hence it is a social necessity. It comes as no surprise that the relationship of religion to the ummah is like that of the heart to the body. Nowadays we see that there are many religions in the world, and each people has its religion which they cling to. What is the true religion which will fulfil the aspirations of the human soul? What are the guidelines of the true religion? 
And Allah knows best.