Final answer:
The most important function of humanism, according to Venetian humanists like Francesco Negri, was to improve individuals and societies through the study of ancient Greek and Roman philosophy, history, and literature.
Step-by-step explanation:
According to Francesco Negri and other Venetian humanists, the most important function of humanism was to improve individuals and societies through the study of philosophy, history, and literature from ancient Greece and Rome. Humanists believed that by immersing themselves in the wisdom and achievements of the classical world, they could enhance their understanding of human nature and live a better life.