I think that the Reformed Approach to Theology, as shown by its attitude about Jesus’ presence in the Eucharist and about Holy relics in particular, eventually could lead out of Biblical Christianity. Its idea of sola scriptura really is about an arbitrary reading of scripture where anyone can claim they have the “true” meaning and don’t have to be chained to what other Christians teach or have taught (Tradition) about the Bible. The Calvinist reading of scripture on the Eucharist is very naturalistic and uses “the ordinary laws of nature” as Calvin put it in his Institutes, to reject the Lutheran and traditional view of the Eucharist and Christ’s bodies. Once you go down that route, the resurrection itself and Jesus’ ascension are under question for violating natural laws. Likewise he considers relics to be “Superstition”.
Of course, the plain meaning of the Eucharist in scripture is that the food actually is Christ’s body like Catholics and Lutherans teach in one way or another. And holy objects and relics are mentioned numerous times in both Testaments. But for Calvin, who started his religion in the Enlightenment era, the “ordinary laws of nature” can trump the plain meaning of scripture and he doesn’t have to conform to the way the rest of the Christians (the Church) understand the Bible. So eventually Protestants like Marcus Borg or A.R.Eckardt can claim that Jesus’ miracles like resurrection were just an allegory or give other reasons for claiming that it didn’t actually happen.
Thank goodness for Protestantism!
Yes, I agree, Protestantism opened the door to a more personal (and more critical) evaluation of the Bible and the claims of Christianity. Prior to Luther (and Calvin) Christians simply believed what they were told. Protestantism allowed Christians to (begin, at least, to) think for themselves. Yes, it split the Church into dozens if not hundreds of denominations and sects, but it did liberate western culture from the iron grip of Rome, leading to freedom of religion, freedom of conscious, and eventually, freedom of speech.
Secularism/atheism owes a great deal of debt to the Protestants.
I shudder to think what western civilization would look like if Martin Luther had not nailed his Ninety-Five Theses to the door of that church in Wittenberg, 499 years ago.