"If your Lord had so willed he could have made humanity one people, but they will not cease to disagree, except those on whom your Lord has bestowed His mercy." [Sûrah Hûd: 118-119]

In an earlier article of mine under the same title, I wrote about this verse:
…it is possible that Allah is not only referring to the fundamental disagreement between believers and unbelievers. He may also be alluding to the differences that exist within the ranks of the believers themselves. Some believers are pious and devout, avoiding sin to the utmost extent humanly possible. Others are weak and easily fall victim to their base desires. In this context, Allah's words: "Except those on whom your Lord has bestowed his mercy" refer to those Muslims who abstain from sin and only disagree with each other in matters wherein Islamic Law permits disagreement.
It is this topic of permissible and impermissible disagreement that I wish to focus on in the present article.

Allah has made disagreement a reality of life. In spite of how natural disagreement is to the human condition, people are clearly discomfited by it. How often have we heard these plaintive questions: When will the scholars stop disagreeing with each other? How long will the Muslims persist in disagreeing on this issue?

The answer to these questions is: Disagreement will remain part of life until Allah inherits the Earth and everyone on it. We should not nurture the hope that people will come to some global consensus. Allah tells us: "but they will not cease to disagree." [Sûrah Hûd: 118] This verse tells us that disagreement is something Allah has decreed to exist in our world. It is a reality of life.

Indeed, from the perspective of Islamic teachings, disagreement is not always bad. Sometimes it is praiseworthy, and sometimes it is blameworthy.

The most blameworthy type of disagreement is division and disunity. Division and discord are never praiseworthy. This should be clearly distinguished from disagreements in point of view or in understanding, which might be praiseworthy or blameworthy depending on the circumstances surrounding the disagreement. It should also be distinguished from practical differences, where one person employs his or her efforts to a certain task while someone else focuses on another task.

Division where people become polarized into antagonistic groups is always bad. The Prophet (peace be upon him) warned the Muslims against this when he said: "My community will divide into 73 sects, and all of them will be in the Hellfire save one." [Sunan al-TirmidhîSunan Ibn Mâjah (3991, 3993)]

Allah says: "Be not like those who are divided amongst themselves…" [Sûrah Al `Imrân: 105]

This is a clear prohibition of becoming divided. However, the verse continues: "…and disagree after clear evidence has come to them." This indicates that disagreements encompass that which is acceptable and unacceptable – or at the very least, the disagreement might be excusable or inexcusable.

This is obvious when the disagreement has a sound basis for it. Any party to such a disagreement will either be in a praiseworthy position, or in one where he or she at least has an excuse for adopting the particular stance.

It is because of this that the Prophet (peace be upon him) said: "If a judge gives a ruling, exercising his best judgment, and he is correct, the he will receive a double blessing If he gives a ruling, exercising his best judgment, and makes a mistake, then he will receive a single blessing." [Sahîh al-Bukhârî (7352) and Sahîh Muslim (1716)]

Observe how the Prophet (peace be upon him) explicitly says he "makes a mistake". In spite of being mistaken, he receives a single blessing for exercising his best judgment (ijtihâd). This is Allah's mercy. If a person who is sufficiently qualified in knowledge exercises his or her best judgment, then the effort is blessed, whether her or she gets it right or makes a mistake. In this way, Allah encourages us to exercise our judgment in matters wherein we possess sufficient knowledge and proficiency. He encourages us by promising us blessings for doing so, even if we make a mistake.

Such disagreements are praiseworthy as long as they based on legitimate arguments and evidence, where those who hold differing opinions do so sincerely after exercising their best efforts to arrive at the truth. By contrast, disagreements based on vain desires, vested interests, and arrogance are blameworthy. Such disagreements lead people to become polarized and divided among themselves.

There is, finally, another way that people differ which is certainly praiseworthy. This is where people opt to devote their efforts to various good things. Consider Islamic work. Some people focus on Islamic legal matters. Others engage in calling people to righteousness. Some seek to reconcile people and bring about peace. Others deal with family matters and domestic problems. Still others engage in relief work. Some teach. Some build mosques. The list goes on. Such differences only serve to enrich and strengthen society.

And Allah knows best.