The Noble Prophet is ruler over the entire creation; similarly, Imām Mahdī is ruler over the entire creation. The former is the Seal of the Prophets while the latter is the Seal of the Imāms. The former is the general guardian by nature while the latter is the general guardian by delegati
(Sahifeh-ye-Imam, Vol.20, page 233)
It is not such that when we wait for reappearance of the Imām of the Time (PBUH), we should sit at home, pray for his reappearance. His reappearance should be hastened through your struggle... To prepare the ground is achieved by bringing Muslims together and get them united. God willing, he will reappear.
Sahifeh-ye-Imam, Vol.18, page 221
All Ibrahimi religions believe in an end-times savior. All Ibrahimi religions believe that someone will emerge who will save the world from the morass of oppression and cruelty. In Islam, the name of this savior has been mentioned.
All Islamic denominations refer to this divine person and this great and extraordinary individual as Mahdi. Perhaps, there is no Islamic denomination that does not believe Mahdi (peace be upon him) will emerge.
He is a descendent of the Holy Prophet (peace be upon him). Islamic denominations have even specified the name and epithet of that Hazrat. The characteristic of Shia ideology is that it completely and clearly introduces this personality.
It considers him as the son of the eleventh Imam - Hazrat Imam Hassan Askari (greetings be upon him).
From the viewpoint of Shia historians and writers, his birth date is completely clear. Most of other Islamic denominations have not specified his birth date or they have not accepted it, but the Shia prove the existence and birth date of that great personality with strong and cogent reasons.
Some people have dismissed the possibility of the existence and survival of a person over this long time.
This is the only question that opponents have raised regarding the issue of Hazrat Mahdi (a.s.). However, the Holy Quran dispels this doubt with its clear words. The Holy Prophet (peace be upon him) says about Hazrat Nuh, "We sent Nuh to his people, and he tarried among them a thousand years less fifty" [The Holy Quran, 29: 14].
This does not mean that he lived for 950 years. It apparently means that his mission - to invite people to God - lasted for 950 years. Therefore, this questioning is groundless.
Today, only those count as the true supporters of Mahdaviat (i.e. the concept of waiting for Mahdi, our savior, the twelfth Shiite Imam otherwise known as Imam Zaman, and Zaman meaning time) and the coming of the Peacemaker, who put their efforts in establishing world peace and are the promoters of democracy and human rights. Moreover their movement should be into the path of science and knowledge.
In the school of Mahdaviat, neither soothsaying and geomancy, nor dreams and superstition, but only freedom of thought and reason count as giving service to humanity and to the advancement of science and knowledge.
On this same basis, at the time of the coming of Mahdi (May God Almighty hasten his appearance), the rule of the people and peace shall govern the day and any one who should want to confront the freedom of thought and speech is, in fact, working against the coming of the Promised Mahdi (May God Almighty hasten his appearance ).