This article focuses on John Wycliffe´s thought and aims at uncovering an inherent revolutionary potential of his philosophy. First, Wycliffe´s metaphysical realism that gave rise to a specific notion of truth based on the divine authority is examined. This notion is then developed into a belief that the Scripture is the absolute authority in the matters of truth. Therefore, Wycliffe considers the Biblical description of the First Church to be a measure for all other ages. However, the Church in Wycliffe´s time was far away from this ideal – thus he concludes that the present day Church needs to be reformed. Since even the Pope, the very head of the Church is corrupt, the reform must come from outside of the Church, namely from the King.