The Society of Jesus, commonly known as the Jesuits, was founded in 1534 by a group of University of Paris graduate students led by Iñigo Lopez de Loyola, known more commonly by the Latin version of his name, Ignatius of Loyola. The Society's organization was approved in 1540 by Pope Paul III.
The Jesuits were founded as part of the Catholic Reformation, a reactionary movement to the Protestant Reformation, whose heresy was sweeping Catholic Europe. They preached total obedience to scripture and Church doctrine, Ignatius Loyola himself declaring that -
One of the main tools of the Jesuits was the Ignatian retreat. In this, people would come together under a Priest for a week, or even for 5 weeks. During this time, they would remain silent while attending confrences and undergoing exercises to make themselves a better person. For example, there are confrences and meditations on our immanent deaths, etc.
They also preached that the ceremony and decoration of organized Catholicism (which the Lutherans so despised) should be lavishly financed and executed.
The Jesuits were able to obtain significant influence in the Early Modern Period because Jesuit priests often acted as confessors to the Kings of the time. They were the leading force in the Counter-Reformation, in part because of their relatively loose structure (without the requirements of living in community, saying the holy office, etc.) allowed them to be flexible to the needs of the people at the time.
Their motto is "Ad Majorem Dei Gloriam," a Latin phrase, often abbreviated AMDG, which means "for the greater glory of God." This phrase is designed to reflect the idea that any work thats not evil can be meritorious for heaven if it is performed with this intention, even things considered normally indifferent like filling up a gas tank in a car.
Among many distinguished early Jesuits was St. Francis Xavier, missionary to asia who converted more people to Catholicism then anyone since St. Paul.
Jesuit missions in Latin America were very controversial in Europe, especially in Spain and Portugal, where they were seen as interfering with the proper colonial enterprises of the royal governments. The Jesuits were often the only thing that saved the Indians from slavery. Together througought South American but especially in Paraguay they formed Christian-Indian city-states, called reductions (Spanish Reducciones). These were societies set up in the ideal Catholic way. It is partly for this reason of protection of the Indians whom certain Spanish wanted to enslave, that they were suppressed.
Other famous Jesuits include: