Martin Luther had certain things in common with the humanists, but I'm not sure that I would call him humanistic in his outlook. Ultimately, the humanists' veneration of classical texts and classical writing was joined with a veneration of the classical world's sense of civic morality. When reading the likes of Cicero, they would tend to focus on his use of argumentation and rhetoric or draw on his example as a great statesman and leader. While they were still religious, the humanists tended to place a much greater focus on the current life, and one's responsibilities within a civic or social community, than the medieval scholastics, who tended to look primarily toward God, did.

That being said, both Luther and the humanists shared a common ground. First and foremost, they both shared a disdain for medieval scholasticism, which they dismissed as artificial and, in many respects, even trivial. Famously, the Protestant formulation of "Sola Scriptura" represented a dramatic break with Christian tradition, stating that theological truth could only be found within the Bible itself, not through the teachings of church tradition. As a result of this viewpoint, Luther also translated the Bible into the vernacular so that the laity could actually read the scripture and not rely solely on intermediaries such as priests. In this, also, Luther paralleled earlier humanists, like Erasmus.

The rallying cry of Renaissance humanism was "Ad fontes!" or "Back to the sources." Renaissance thinkers consciously returned to the treasures of classical learning for inspiration, seeing them as examples to be imitated in a variety of human endeavors, including everything from art and architecture to poetry and political philosophy.

Luther was himself influenced by the humanist veneration of antiquity. However, antiquity for him meant primitive Christianity and the sources he went back to were the Holy Scriptures. In his principle of sola scriptura, Luther insisted that the ultimate truth of things lay in the Bible and nowhere else. Individual Christian believers should interpret the word of God for themselves, instead of relying on the Church to do it for them.

In their privileging of pagan thought, Renaissance humanists often sought to bypass the authority of the Church; they shared with Luther a total disdain for the scholastic philosophy used to provide intellectual support for that authority. However, they still venerated human thought; for Luther, sole authority was vested in the word of God as interpreted by the individual believer.