Final answer:
The sharp disagreement between the Wesleys and George Whitefield was over theological convictions influenced by John Calvin's teachings and Martin Luther's Justification by Faith, resulting in distinct Calvinist and Arminian perspectives in the evangelical movement.
Step-by-step explanation:
The Wesleys and Whitefield strongly disagreed on theological matters influenced by their different religious conversions and affiliations. While both groups were part of the evangelical movement and sought to preach a more personal and emotional form of Christianity, they had distinct theological views. For George Whitefield, John Calvin was the key to his conversion. In contrast, the Wesley brothers, John and Charles, were deeply influenced by the Moravians and the writings of Martin Luther, especially his doctrine of Justification by Faith. This fundamental disagreement in theology, between Calvinist predestination as held by Whitefield and the more Arminian free will perspective espoused by the Wesleys, led to sharp differences in doctrine and practice within the evangelical movement of the 18th century.