The essential unity of the formal and material principles of the Reformation lies in the fact that to affirm that Christianity was, formally and materially, solus Christus was perceived by the Reformers ultimately to depend upon the concurrent affirmation that Christ and his benefits could be known sola scriptura.

For the humanists, whatever authority Scripture might possess derived from the original texts in their original languages, rather than from the Vulgate, which was increasingly recognized as unreliable and inaccurate. In that the catholic church continued to insist that the Vulgate was a doctrinally normative translation, a tension inevitably developed between humanist biblical scholarship and catholic theology...Through immediate access to the original text in the original language, the theologian could wrestle directly with the 'Word of God,' unhindered by 'filters' of glosses and commentaries that placed the views of previous interpreters between the exegete and the text. For the Reformers, 'sacred philology' provided the key by means of which the theologian could break free from the confines of medieval exegesis and return ad fontes to the title deeds of the Christian faith rather than their medieval expressions, to forge once more the authentic theology of the early church.

The medieval period based its scriptural exegesis upon the Vulgate translation of the Bible. There was no authorized version of this text, despite the clear need for a standardized text that had been carefully checked against its Hebrew and Greek originals. A number of versions of the text were in circulation, their divergences generally being overlooked. It was not until 1592 than an 'official' version of the text was produced by the church authorities, sensitive to the challenges to the authority of the Vulgate by Renaissance humanist scholars and Protestant theologians.

In short, an astonishingly broad spectrum of theologies of justification existed in the later medieval period, encompassing practically every option that had not been specifically condemned as heretical by the Council of Carthage. In the absence of any definitive magisterial pronouncement concerning which of these options (or even what range of options) could be considered authentically catholic, it was left to each theologian to reach his own decision in this matter. A self-perpetuating doctrinal pluralism was thus an inevitability.

The rising influence of lay piety is particularly marked upon the Mariological controversies of the late medieval period. Two rival positions developed: the maculist position, which held that Mary was subject to original sin, in common with every other human being; and the immaculist position, which held that contrary view that Mary was in some way preserved from original sin, and was thus to be considered sinless. The maculist position was regarded as firmly established within the High Scholasticism of the thirteenth century. The veneration of the Virgin within popular piety, however, proved to have an enormously creative power that initially challenged, and subsequently triumphed over, the academic objections raised against it by university theologians.