After the death of the Prophet, the Imam was entrusted with the guardianship of his accomplishments and the continuation of his leadership, in order to teach men the truths of the Qur'an and religion and ordinances concerning society; in short, he was to guide them in all dimensions of their existence. Such leadership, exercised in its true and proper form, is nothing other than the realization of the goals of Islam and the implementation of its precepts, precepts established by the Messenger of God; it bestows objective existence on the ideal of forming a community and codifying a law for its governance. Imamate and leadership are sometimes understood in a restricted sense to refer to the person who is entrusted with exclusively social or political leadership.
However, the spiritual dimension of man is connected intimately with the mission of religion, and the true and veritable Imam is that exalted person who combines in himself intellectual authority and political leadership; who stands at the head of Islamic society, being enabled thereby both of convey to men the divine laws that exist in every sphere and to implement them; and who preserves the collective identity and the human dignity of the Muslims from decline and corruption. In addition, the Imam is one whose personality, already in this world, has a divine aspect; his dealings with God and man, his implementation of all the devotional, ethical and social precepts of God's religion, furnish a complete pattern and model for imitation. It is the Imam who guides the movement of men toward perfection. It is therefore incumbent on all believers to follow him in all matters, for he is a living exemplar for the development of the self and of society, and his mode of life is the best specimen of virtue for the Islamic community.
Most Sunni scholars are of the opinion that Caliphate (khilafah) and Imamate (imamah) are synonymous, both signifying the heavy social and political responsibility bestowed on the caliph, who attains his position of guardianship for the affairs of the Muslims by election. The caliph both solves the religious problems of the people and assures public security and guards the frontiers of the country through the exercise of military power. The caliph (or Imam) is therefore at one and the same time a leader of conventional type and a ruler concerned with the welfare of society, whose ultimate aim is the establishment of justice and guarding the frontiers of the country, it is for the sake of these aims that he is elected.
According to this concept, the qualifications for leadership are governmental competence and capacity for rule. On the one hand, the leader must punish errant and corrupt individuals by implementing the penalties God has decreed; hold in check those who would transgress against the rights of others; and repress rebellious and anarchic ruffians. On the other hand, by acquiring the necessary military equipment and organizing a powerful army, he must both protect the frontiers of the Islamic state against all aggression, and also confront, with jihad and armed struggle, various forms of shirk and corruption and factors of ignorance and unbelief if they prevent the progress or the implementation of true religion and the dissemination of tawhid by way of propagation and guidance powers proves impossible.
In this view of things, it does not present a major problem if the leader or ruler has no background of erudition with respect to God's ordinances, or even if he has strayed beyond the boundaries of piety and polluted himself with sin. Anyone can lay claim to the title of successor (khalifah) to the Prophet who undertakes the tasks he used to fulfil. It is not offensive if some oppressive tyrant establishes his dominance over Islamic society by trampling the rights of the people, shedding their blood and exercising military force, calling himself the leader of the Muslims; or if some twofaced politician assumes the office of successor to the Prophet, and then proceeds to rule over people, despite his lack of spiritual and moral qualities, canceling all notion of justice and equity. Indeed, not only is it impermissible to oppose him; it is necessary to obey him.
It is on the basis of this view of the matter that one of the great Sunni scholars expressed himself as follows concerning the caliph: "The caliph cannot be removed from office on account of contravening God's laws and commands, transgressing against the property of individuals or killing them, or suspending the laws God has decreed. In such a case, it is the duty of the Islamic community to set his misdeeds aright and to draw him onto the path of true guidance." However, if such an atmosphere predominates in the institution of the caliphate, with the caliph leaving no sense of responsibility, based on his own religiosity, toward Muslim society, how can those who wish to reform the situation constantly watch over the deeds of a corrupt leadership, evince the appropriate reaction on every occasion, and purge Islam of deviation? Can rulers be persuaded by mere advice to change their ways?
If God had wished to entrust the destinies of the community to unworthy rulers, to impious and selfish oppressors, it would not have been necessary for him to bestow messengerhood on the Prophet or to reveal the ordinances needed for the stability of society. Did those caring, self-sacrificing and noble souls who throughout the centuries rebelled against evil and oppressive rulers act contrary to God's will? After the Messenger of God, the Islamic ummah stood in need of a worthy personage who would be endowed with the knowledge derived from revelation, exempt from sin and impurity, and capable of perpetuating the path of the founder of the shari'ah. Only such a personage would be able not only to watch over the political developments of the time and to protect society from its deviant elements, but also to provide people with the extensive religious knowledge which spring from the fountainhead of revelation and derive from the general principles of the shari'ah. The laws derived from revelation would thus be preserved, and the torch of truth and justice held high.