During the Middle Ages knowledge was based on authority, which was not to be questioned. That authority consisted of the Bible and Aristotle. Interpretations of the Bible were also not to be questioned. The text of the Bible in use at that time, the Vulgate, had been translated by St. Jerome, and as he was a saint, was considered unassailable. Experimentation was discouraged, as experimentation led to error, error to sin, and sin to damnation. Human beings were considered imperfect creatures who toiled through life with the hope and expectation of reward in the next life. Art of the period shows no perspective or emotion; rather people are often shown almost as cartoon characters.
Renaissance scholars did in fact question the authority which was earlier considered sacrosanct. Many preferred reading the classics, including Aristotle, in the original languages. This included the Bible in the original Greek and Hebrew. One Renaissance thinker, Desiderious Erasmus, re-translated the Bible and found numerous errors in the Vulgate. Scholars of this period also believed that rather than corrupt creatures, humans were God's greatest creation, and should be celebrated. This also is evident in the art of the period, which shows human beings realistically, often with classical tones. The belief that knowledge made a man free, led to the development of the Humanities as a course of study. Because the humanities made one free, they became known as the Liberal Arts.
The characteristics of the Renaissance can be seen as a rebellion against the characteristics of the Middle Ages, which overturned concepts of the Middle Ages.
The Middle Ages were a time in which religion dominated everything. Art and literature and scholarship were all centered around the Catholic Church and around the idea of glorifying God. Human beings were not seen as very important in and of themselves.
Though we should not overstate this, things changed in the Renaissance. Religion was still very important. However, there was much more of a move away from accepting religious authority. People started to believe in the tenets of humanism. They started to seek scientific proof of various things instead of accepting received wisdom. This was a time that was coming to focus on people rather than on God.
In this way, the characteristics of the Renaissance can be seen as a rebellion against and a repudiation (within limits) of the old ways.