The content of Luther’s doctrines cannot be overlooked when considering the cause of his popularity however the extent to which the average Christian could understand the large volume of highly intellectual and complex doctrines is relatively limited. The inaccessibility of Luther’s work made a large proportion of his doctrine incomprehensible to the laity. However, the reproduction of his works was only made possible by their demand. The 95 theses swiftly grasped the attention of academics across German lands. This academic attention led to Humanists analysing his works. Martin Luther’s emphasis on sola scripture and the corruption of the Roman Catholic Church were the key motifs for the production of pamphlets. The work published by Luther in 1520, On the Liberty of a Christian contained doctrine which started the works on sola scripture. This work emphasised the importance of Justification by Faith. Luther reinterpreted a text from Romans 1:17, which stated that ‘the righteousness of God is revealed through faith for faith, “he who through faith is righteous shall live.” Luther interpreted this to mean that God only justified, or made righteous, those who had faith, ‘Therefore it is clear that, as the soul needs only the Word of God for its life and righteousness, so it is justified by faith alone and not by any works’. Luther’s doctrine of justification removed the need for the late medieval system of sacraments – there was no place in the reformed teaching for the cycle of sin, sacramental confession, priestly absolutism and ritual penance which had defined the lives of the people since the thirteenth century. The doctrine was a powerful threat to the Church as it allowed the people to rid themselves of anxiety over sin and provided the assurance of salvation despite sin. Previously the Church had a monopoly over salvation but now, through faith and scripture, people could achieve salvation outside of the Church, or at least not have to resort to indulgences (which would require a large chunk of a laymen’s annual income), pilgrimages or acts of piety. This radical split from Catholic doctrine provided the laity with a solid reason to separate themselves from Catholicism and become a follower of Lutheranism. To convert to a different religion was a huge decision, which required a person to be certain of their choice and to believe that the conversion would improve their current circumstances. Luther explains why his doctrine on Justification is important, in a source from the Doctrine of the Two Kingdoms.