There have been few cultural movements as mutually sustaining and as diametrically opposed as the Renaissance and the Reformation. Coming on the heels of the Medieval era, both constituted responses to the supremacy of the Church—the first to the Church's appeals to tradition over reason, the second to the Church's insistence on its own authority over that of Scripture. The Renaissance and the Reformation both needed each other, but found little ground for cooperation or agreement.
When we speak of the Church in this context we're speaking not of the universal Church that constitutes Christ's body, but of the Roman Catholic Church headquartered in Rome and for several centuries the broker of spiritual authority everywhere the Gospel had been preached. Philosophy took a sharp turn after Aquinas, and instead of simply accepting Church dogma as the starting place for all intellectual inquiry, thinkers adopted a more anthropocentric (man-centered) attitude.
Eventually this would look like Descartes positing himself as the chief referent for all perceived reality (and thereby laying the foundation for philosophical solipsism and existentialism), but for the Renaissance thinkers it meant rooting their ideas in the works of Classical authors like Aristotle and Plato, and using inquiry as the basis for intellectual progress. Many of them still professed allegiance to Christianity (many for political reasons), but their true allegiences lay elsewhere. Wisdom was no longer the basis for philosophy; Truth was, and since the Church couldn't necessarily be trusted as the source of truth, man would have to construct his own using only his mental capacities.
These attitudes would become much more realized during the Enlightenment, but everything Rousseau and his ilk thought up had been established by their Renaissance forebears. The appeals to reason didn't have entirely negative effects, however. Men of God began investigating the Scriptures for themselves (formerly the sole province of certain Church theologians), and realized the true authority for Christian belief and practice was Christ as mediated through His Word, not the papacy or Church hierarchy (which, moreover, had as much clout in the temporal realm as the spiritual).
In a series of acts that may have been taken from any dramatic novel, Martin Luther laid the groundwork for the Protestant Reformation. Not least of his efforts was to interpret Scripture by the rubric of salvation by faith alone, thus controverting the Church's claims as the locus of salvific work. Luther (a bona fide genius) was soon followed by others (also bona fide geniuses mostly), and the beginnings of the separation of Church and State were formed in the sense that there was a move away from State-sponsored churches toward independent institutions of worship and discipleship.
A state of conflict this extreme historically either kills literary output for a time, or fans the flames of creativity to conflagration status. The Renaissance and Reformation had the latter effect, and soon Europe was burning with some of the greatest works the world has ever seen. Writers were still concerned with imparting ideas (perhaps more than ever), but they were also more directly concerned with the construction of the langauge and the musicality of words.
Who were these craftsmen, you may ask? William Shakespeare. Edmund Spenser. Desiderius Erasmus. Christopher Marlowe. Get the picture? Even Martin Luther and John Calvin penned works of enduring literary and theological significance. It was a time of change, of adherence to excellence, of great intellectual fervor and activity. It was the age of Galileo and da Vinci and Michelangelo. It was a glorious age in Europe!
Like all ages of men, it didn't last. Yet the twin flames (or spectres, depending on your perspective) of the Renaissance and the Reformation continue to guide thought, literature and religious practice all over the world. Some of the greatest works of all time were written during this (chronologically rather vague) era, and any student of literature and ideas needs to immerse himself in the writings each movement produced if he is to call himself educated, or thinks he understands the current situation. Currently our selection is a bit Shakespeare-heavy, but we're working on that.