It has been called ummul-amraadh, or the root of all sicknesses of the heart. Prophet Muhammad, sallallahu alayhi wasallam, warned that a person having even an iota of it in his heart will never enter Paradise. This deadliest of all sins is kibr, or arrogance.
No one likes arrogance --- in others. We never like a person who is haughty, too proud, or condescending. We detest a person who belittles us and has a huge ego. Similarly we love people who are humble, polite, and easy to talk to. We love people who give us respect and honor. Thus if we follow the principle of treating others the way we like to be treated, most of these problems might be cured. In reality, the treatment of ummul-amradh requires a deeper look.
For that we need to appreciate the difference between Aadaab or manners, on the one hand and Akhlaq or morals on the other. While adab deal with one's external disposition, akhlaq as defined by Islam deals with our inner thoughts, feeling, and attitudes. In a healthy personality, manners and morals are in harmony. But it is also possible to have the former without having the latter. The first concerns itself with how a person deals with others. The second is concerned with what a person thinks of himself. Two persons showing humbleness in their dealings with others, may have exactly opposite ideas in their minds. One may do it out of his or her "generosity"; the other may do it because he genuinely thinks that he is not better than the other person. The first person only has a shell of humbleness, which will crumble when tested. It is the second person who is really free of arrogance.
Real greatness belongs only to Allah, our Lord, Creator, and Master. Human beings are just a creation of Allah --- and a very small creation in comparison to the unimaginably vast universe He has created. Anyone who understands this will realize that our proper status is only that of servants of Allah. In fact for a Muslim the real human model is none other than Prophet Muhammad, sallallahu 'alaihi wasallam, who is the greatest of all human beings. His greatness lies in being the humblest of all servants of Allah! It is impossible for any person who has this consciousness to entertain any notion of his own greatness.
This leads us to the definition of kibr, given in a famous hadith: "Kibr is to knowingly reject Truth and to belittle other people." This hadith exposes two strains of this deadly disease, both dealing with our exaggerated ideas of self-importance. The first suggests that I am more important than the Truth. The second suggests that I am more important than other people.
We know about the Quraish and Jews of Arabia who had come in contact with Prophet Muhammad, sallallahu alayhi wasallam, and who knew in the heart of their hearts that he indeed was the Messenger of Allah. Their arrogance, though, kept them from accepting it. History has recorded statements from some of them who said we know he is the Promised Prophet but we will keep on opposing him to maintain our leadership.
While that was the most blatant form of arrogance, we can witness the same attitude on a smaller scale in our own discussions and arguments. A person realizes that he is wrong, but then his pride keeps him from admitting it. No matter how polite or "humble" that person may appear to be ordinarily, this test shows the presence of arrogance in his heart. It is arrogance that keeps a person from saying "I am sorry."
The second strain involves our feeling of superiority with respect to other people. Islam teaches us that one should never consider oneself greater than other people, because that judgment will come from Allah, and Allah alone, on the Day of Judgment. None of us knows what our end will be, whether we will end up being a winner or loser over there. The person who appears to be nobody here may end up with eternal bliss because of his goodness that only Allah knew. The person who is a big shot here may end up among the sinners who will be punished there, because of his evil that only Allah knew. How foolish, it is then to congratulate ourselves over our fleeting "superiority".
What if a person does have an edge over another person in measurable worldly terms? How then can he not consider himself superior than the other person in that respect? The point is sometimes made in half jest: it is difficult to be humble when you are so great. Islam does not ask us to reject reality and imagine we don't have what we really do. Rather it asks us to take a deeper look at the reality and not be misled by a superficial perception of it. And the simple reality that escapes many is that our health, wealth, talents, and power are not of our own creation. God gave those to us as a test and He can take them back whenever He wills. Those who are conscious of this reality, their blessings will produce gratitude in them; those who are blind to it will develop pride and arrogance.
Some forms of kibr are subtle. If a person is embarrassed to bow to Allah in the presence of non-believers, that is a case of "kibr in the face of Allah," says Maulana Ashraf Ali Thanvi.
While throughout history humanity had agreed on the evil of arrogance and the virtue of humbleness (despite its failures in practice), but this century has seen new dogmas that aim at changing the definitions of good and evil. Humbleness is no longer desirable. Rather, one has to avoid "Inferiority Complex." Alfred Adler (1870-1937) gave us that term. According to him, life is a continuous struggle to move from a position of inferiority to a position of significance. Those who fail to make the progress, develop inferiority complex, which can be treated by increasing self-esteem. Unfortunately today such pseudo-science is accepted as gospel truth.
The truth is that problems arise when we turn away from reality. A humble person is a happy, contented, grateful person who thanks God for His blessings and has no notion of his own superiority. False notions of superiority or of one's entitlements in life, on the other hand, lead to frustrations and complexes.