The Renaissance, particularly in its origins in Italy, was characterized first by a new commitment to the spirit of humanism. Humanism was, essentially, based on the study of the classics, both the Greeks and the Romans, and it was framed by Renaissance thinkers as a way of breaking away from what they thought of as the "dark ages" of medieval Europe. Almost all of the important Renaissance writers, including Machiavelli, Pico Della Mirandola, Lorenzo Valla and Leonardo Bruni wrote within the humanist tradition.
Renaissance thinkers also stressed individual achievement, especially in secular pursuits. For the first time since Roman times, artists and architects were viewed as public figures who should be celebrated, and individuals were measured by the breadth of their accomplishments. The "Renaissance man," was, simply speaking, good at everything, and this was something to be pursued not just for the glory of God, but as a means of achieving fame and fortune. It was in this context that learning about the world through observational science first became a major emphasis.
Finally, the Italian Renaissance was characterized by great artworks that emphasized balance, proportion, and harmony. All of these principles had been important in the classical world, but were largely neglected during the Middle Ages. The achievement of these ends demanded a high degree of technical skill on the part of the artist.