The Crusaders' dissemination of the newly discovered Greek and Roman writings helped spur a new interest in these pagan writings that glorified the human being (especially the Greeks).  In the universities, especially in Italy, a more secular education began to develop.  This coincided with several calamities of the church, including the Avignon Exile and the Great Schism, which greatly damaged the pope's prestige.  The Italian poet Francis Petrarch compared the Avignon Exile to the Babylonian Exile, when Jewish leaders were exiled to Babylon, a center of material wealth and decadence, in 6th c. B.C.  Italians' proximity with the pope and witness of the pope's many intrigues, their growing wealth and self confidence, all made them reconsider their relationship with God apart from what the pope usually told them.  Starting in late 14th century, they started this quest for a rediscovery of the true identity of the humans, in relation to God, by finding answers from ancient Greek and Roman writings, which was why they called it "Renaissance" or rebirth of ancient Greek and Roman culture.

1. Italy in the 14th-15th centuries

Italy was the most industrialized and wealthiest region in Europe in the 14-15th centuries. Reasons for early Italian development: Trade with Byzantium, the Muslims, and during the Crusades. 

The many practical and professional jobs available in Italy made education more secular. 

Conflicts between Henry IV of the Holy Roman Empire and Pope Gregory VII, between the Houhenstaufens and the popes. Result in Italian politics: decentralization; rivalry between different Italian city-states; and disillusionment with the pope, especially with popes like Alexander VI (r.1492-1503).

Understanding Italy is central to the understanding of the Renaissance.

2. The rise of humanism 

Humanism was a movement to reconsider the relationship between the humans and God.  In medieval Europe, the typical conception of God was He was unlike anything on earth: God was what humans were not.  This negative view of the human being was changed during this reflection on the nature of the humans.  Humanists quoted from the Bible and other sources to vindicate a more positive view of the humans, assigning them a position just a little below the angels.  The individual human being becomes a micro-cosmos because humans were built after the image of God and could express the likeness of God.  Humans were also free to transform themselves.

The result of this positive treatment of the infinite possibilities of the humans was serious studies of the human being, from their lives in the form of stories and histories, their representations through art, to studies of human political behavior free of ethical restrictions, paving the way for later studies in literature, history, politics, philosophy, etc., that, on the whole, are called the "Humanities."

• Treating human lives seriously: Chaucer and the novel.
• Observing human political behavior in a realistic fashion, free of ethical rules: Machiavelli.

Q: What is the difference between "humanism" by the definition in 14th-16th century Italy and today?
 

3. Humanism and medieval studies

Most of the early humanists were educators who were exploring new ways of moral education in a changing age.  They imbued education with much greater emphasis of the study of the human being and focused on individual self improvements. The underlying assumption was that humans could improve themselves, which contrasted with the medieval notion that humans were completely dependent on God for salvation.  Many self-improvement booklets were circulated in Italy.

Q: Can you give an example of such a self-improvement booklet?

Compared with medieval education, Renaissance education focused much more on reading Greek and Roman authors in the original rather than in anthologies.

Later humanists also included secretaries to princes, artists (painters, sculptors) and architects who created art and architecture after Greco/Roman styles. 

Examples:

Niccolo Machiavelli (1469-1527): author of The Prince (homework), was made head of the second chancery (position next to the first chancellor) of the republic of Florence at 29 in 1498. He was initially in charge of internal affairs but later directed foreign relations and defense. His qualities of an ideal prince were based on his observations of ancient Roman politics or his contemporaries, such as Cesare Borgia, son of Pope Alexander VI, who was then attempting to create a principality for himself in central Italy. Inspired by what he thought the strength that came with a unified France, Machiavelli called for a realistic, instead of the traditionally moral or ethical, approach to politics, based on human psychology. This approach, he hoped, would provide a desperate remedy for the desperate ills of Italy.

Baldassare Castiglione (1478-1529): author of The Courtier (homework), was educated by humanists and at the court of (duke) Ludovico Sforza in Milan. He then worked for a marquis in Mantua and the duke of Urbino, serving as the duke's ambassador to Rome in 1513. In 1525 he worked as the pope's ambassador to Spain. The apparent intention of the author in The Courtier was to raise problems (Does a courtier need to be of noble birth? Is his primary occupation warfare? and so on), but many people read other meanings into the book, e.g. how to dress for success.

4. The spread of humanism in Italy

Besides the popularity of the “how to” manuals, and the education of the modern schools, one chief reason for the spread of humanism was rich patronage of the artists and architects. The reason was the result of the decline of feudalism and the rise of new centers of power.

The growth of city-states: Milan, Florence

• Milan: from communal to aristocratic rule. 
• Republic of Florence: from republic to aristocratic rule. Effectively under Medici rule. 
  
  The growth of these city-states and many others, in a changing world where traditional claims for power were often cast aside, led many rulers to enhance their prestige through the patronage of the arts.  Wealth of the patrons led to a flourishing of art, architecture, producing artists such as Lenoardo Da Vinci, Michaelangelo, and Raphael.