One aspect of humanism can be summed up in the Latin phrase, "Ad Fontes." This basically means "back to the sources." Hence, humanism is a desire to go back to the classical world in literature, the arts, and other learning. This aspect can be seen in that the humanists went back to the Greeks and the Romans. In other words, they sought to cut through all the medieval traditions. This caused a flowering of culture and some would say that the humanist even surpassed the Classical world. Whether they did or did not, that is a matter of opinion. What matters is that humanism was a related to the classical world.
The spirit of Renaissance Humanism is often misunderstood as an uncritical glorification of humanity an all good and idealistic portrayal of it. But it is hardly so. Humanism as practised in the Renaissance revitalized the predeterminism-free will debate with the famous Luther-Calvin conflict. Humanity was only seen as a fundamental category which was chozen by the Humanists as a grid through which to explore the world. It was the conception of an anthropocentric universe as opposed to the older theocentric universe, moving from the microcosm to the macrocosm. 'Studia Humanitatis' was the methodology used in the sphere of education by these Humanists. A great emphasis was given on the arts and literature studies, something which has now established itself as the discipline of 'humanities'. There was great focus on rhetorical discourse and the text (Biblical primarily). The Humanists were rigourous textual scholars. They believed in the labour of finding out classical texts and a close textual study to arrive at critical positions.