what were the causes, nature, and results of the italian renaissance? Was it synonymous with humanism, why or why not. How humane was the humanism of the time, why?
The most elemental cause was the revival of Classical science and literature followed by a revival of Classical art. Humanism in the Italian Renaissance was anchored in this revival and its attendant emphasis on studying "humanistic" writings, literature, and art. "Humanistic" in this sense stands in opposition to "divine," which is the study of theology, the study that preoccupied all interest in the Medieval period. The meaning of "Humanism" has expanded much over time and come to mean far more than it originally meant wen the thinkers of the Italian Renaissance rediscovered learning and expression that was not theology-centered.
Just prior to the Renaissance, Italy had become, once again, the major trader between West and East. As trade flourished, the economy grew and fortunes were made. Capital allocation, or banking began in earnest. As more people became wealthy, and didn't have to focus on necessities for survival, their interests turned to the artistic, and the system of patronage expanded. Trading, along with its increased wealth, also unfortunately brought the Bubonic Plague in 1347. The resulting deaths (in some areas one-third died) created an agrarian labor shortage -- demand and cost for labor increased; no farm-hand was ever again tied to the land, and that helped to finally demolish the feudal system. For those who survived the plague and their immediate descendants, the philosophical focus shifted to the enjoyment and comprehension of life. Italy, having its economy restructured, having survived the Plague, and possessing wealth from trade, began the rebirth of Europe.
One of the unintended causes of the Renaissance was that it led to the Protestant Reformation. During the Renaissance, there was a buzz word, "ad fontes." This meant back to the sources. They wanted to bypass the layers of tradition from the Medieval ages and get back to the glories of the classical world. Therefore, during this time, there were great developments in philology and other disciplines surrounding the classical world. In time, this idea of "ad fontes" took root in the church. Protestant wanted to get back to the church fathers and bypass the traditionalism of the Catholic church.
One way to think of the Italian Renaissance was as an effort to find the common ground between Christianity and the teachings of the Greek and Romans, especially the ancient classical philosophers and poets. Using the rubric you have provided, I would then say this:
Cause: one cause was the growing rediscovery of, and interest in, ancient classical texts. For a good recent study of this phenomenon, see The Swerve, by Stephen Greenblatt.
Nature: desire to reconcile Christian teachings with ancient classical ideas. This desire sometimes ran into problems (as Greenblatt shows), but the writings of Petrarch (for example) are far more typical of the Renaissance than the writings Greenblatt examines. Petrarch is perhaps the best exemplar of a "Renaissance man" in almost all the senses of that term.
Results: a growing number of texts and thinkers who were educated in the classics and saw the relevance of the classics to their lives as Christians.
Humanism: a growing emphasis on living virtuous lives in the here and now, as members of civic communities, rather than focusing as strongly as in the past on the importance of the heavenly (or hellish) afterlife.
The Italian Renaissance principally concerned a move away from the ignorance of man and trust in divine realities towards a recognition of man's ability to use his reason and intelligence to understand the world around him rather than relying on supernatural explanations for the world.
The Italian Renaissance was basically a cultural change. It was a change from a focus on the supernatural to a focus on rationality and human beings. We can see this, for example, in the paintings of the time in which there was a much greater emphasis on the human form (think Michelangelo" even though the paintings were of religious subjects.