Many people have narrated from the prophet concerning the reappearance at the end of the time, of the Mahdi who is a descendent of his daughter Fatimah, and how he will spread justice and equity throughout the world, after it has been overcome by injustice and oppression. All sects of Muslims have accepted this good tiding, but with different interpretations.
It is not a new opinion or idea that has come into existence only among the Shi'a, and in which they were prompted to believe by oppression, dreaming of someone who would come to clear the world of injustice, as some malevolent sophists have suggested. On the contrary, the concept of the reappearance of the Mahdi has been well known among all Muslims, and they have believed in it.

Proof of this is that some persons falsely called themselves Mahdi during the first century after the advent of Islam; such were the leaders of the Kaysaniyyah;s the `Abbasids and the `Alawiyyah.

Only because people believed in the Mahdi could these persons have deceived them, exploited their belief and seized power. So they made their claims in order to impress the people and spread their influence.

We, the Shi'a, on the one hand, believe in the truth of the Islamic religion as the last Divine religion, and have no expectation of another religion to come and reform humanity. But, on the other hand, we observe oppression and corruption spreading day by day throughout the world, resulting in a total lack of justice and improvement anywhere in the inhabitable countries of the globe.

We have also witnessed Muslims foresaking every Islamic principle, commandment and law in every single Islamic country.

We know that we must wait for the reestablishment of Islam in all its power, to reform this world, drowned as it is in oppression and corruption.

Naturally, with such diversity of opinion among people pretending to be Muslim as we see today, it is impossible that the superiority of Islam should return, unless a great reformer appears to protect it, and, through Divine providence, unite people and eradicate the error, perversion and wrong which has become admixed with Islam. To be sure, this guide must possess such a great position, such general authority and such supernatural power as to fill the earth with justice and equity when it is full of evil, injustice and wrong.
In short, the observation that humanity is in a pitiful condition, the assertion of the truth of Islam, and its position as the last religion leads to the expectation of such a great reformer (mahdi) to bring salvation to the world.

All Muslim sects and the peoples of other religions believe in this expectation, the difference being that the Imamate sect believes that this reformer is a definite person, that he is the Mahdi, and that he was born in 256 A.H. (870 A.D.), that he is alive now, the son of Imam Hasan al `Askari, and that his name is Muhammad.

Many narrators have passed to us ahadith (pl. of hadith) from the Prophet and his Household concerning his birth and his absence.

The Imamate must continue uninterrupted, although the Imam may live hidden among mankind until Allah wills that he reappear on a certain day, a Divine mystery known only to Him. The fact that he has lived for such a long time is a miracle granted to him by Allah, and it is no more amazing than the miracle of the start of his Imamate for humanity at the age of five, when his father's life was taken away. Nor is it any more surprising than the miracle whereby `Isa talked with people from his cradle, and was appointed a prophet when still an infant. From the physiological point of view, it is quite certain that to live more than the natural span of life, or more than the imagined natural span, is not impossible, even though medical science is not yet able to prolong human life as much as possible.

But while medicine is unable to do this, Allah can, for He is All-Powerful and Omnipotent. For the Qur'an states that Nuh lived to a very old age, and that `Isa is alive now, and once one has accepted Islam, there can be no denying what the Qur'an says. It is incomprehensible that a Muslim should dispute the possibility of these things, while at the same time calling himself a believer in the Glorious Qur'an.

We should remember at this point that the expectation of this saviour and reformer, the Mahdi, does not mean that Muslims should stand idle in their religion, or abandon their religious duties, but that they should perform all the Divine commandments and make every endeavour to seek out the way of Truth.

It is an obligation for them to fight for Islam, to put the principles of Islam into practice, to order others to do likewise and to prohibit them as far as possible from doing wrong. As the Prophet said:

"Every one of you is a shepherd, and every one is responsible for his flock."
Therefore it is wrong for a Muslim to pay no attention to his religious duties, and to abandon them because he is expecting the Mahdi, the one who brings good tidings; because such an expectation must not induce us to have no responsibility or duty, or to postpone any of our actions, and it will not leave people aimless like animals