It is a historical irony that the Reformation created a political and religious culture in northern Europe that was especially hostile to the spirit of free inquiry and scholarship that characterized Humanism. Why? Because the Protestant Reformation owed so much to the developments of Humanism and the work done by humanists to change how people thought.
In the first place, a principle aspect of humanist thought involved critiques of the forms and dogmas of medieval Christianity. Humanists objected to the manner in which the Church controlled what people were able to study, repressed what people were able to publish, and limited the sorts of things people could even discuss amongst each other.
Many humanists, like Erasmus, argued that the Christianity which people experienced was nothing at all like the Christianity experienced by the early Christians or taught by Jesus Christ. These scholars relied heavily upon information gathered directly from the Bible itself and even worked to produce improved editions of the Bible along with translations of the early Church Fathers, otherwise only available in Greek and Latin.
All of this, obviously enough, has very close parallels with the work done by Protestant reformers barely a century later. They, too, objected to how the structure of the Church tended towards repression. They, too, decided that they would have access to a more authentic and appropriate Christianity by paying more attention to the words in the Bible than the traditions handed to them by religious authorities. They, too, worked to create better editions of the Bible, translating it into vernacular languages so that everyone could have equal access to their own sacred scriptures.
This brings us to another important aspect of Humanism which was carried over into the Reformation: the principle that ideas and learning should be available to all people, not simply a few elite who might use their authority to restrict the learning of others. For humanists, this was a principle to be applied widely in that manuscripts of all types were translated and eventually printed cheaply on the presses, allowing almost anyone to have access to the wisdom and ideas of ancient Greeks and Romans.
Protestant leaders did not show quite so much interest in pagan authors, but they were keenly interested in having the Bible translated and printed so that all Christians might have an opportunity to read it for themselves a situation that presupposed the widespread learning and education which had long been promoted by humanists themselves.
Despite such important commonalities, Humanism and the Protestant Reformation were unable to make any sort of real alliance. For one thing, the Protestant emphasis on early Christian experiences led them to increase their teaching of the idea that this world is nothing more than a preparation for the Kingdom of God in the next life, something that was anathema to humanists, who promoted the idea of living and enjoying this life here and now. For another, the humanist principle of free inquiry and anti-authoritarian critiques was bound to be turned upon Protestant leaders once they were as firmly established in power as the Roman Catholic leaders were previously.
The ambiguous relationship between Humanism and Protestantism can be seen quite clearly in the writings of Erasmus, one of Europes most noted humanist philosophers and scholars. On the one hand, Erasmus was critical of Roman Catholicism and the ways in which it tended to obscure early Christian teachings for example, he once wrote to Pope Hadrian VI that he could find a hundred passages where St. Paul seems to teach the doctrines which they condemn in Luther. On the other hand, he rejected much of the extremism and emotionalism of the Reformation, writing at one point that Luthers movement was not connected with learning.
Perhaps because of the consequence of this early relationship, Protestantism has taken two different routes over time. On the one hand we have had a Protestantism which has focused upon adherents the more emotional and dogmatic aspects of the Christian tradition, giving us today what is commonly called fundamentalist Christianity. On the other hand we have also had a Protestantism which has focused upon rationalistic studies of Christian tradition and which has valued the spirit of free inquiry, even when it contradicts commonly held Christian beliefs and dogmas, giving us the more liberal Christian denominations we see today.