John Wesley (June, 28 1703 – March 2, 1791) was an Anglican cleric and Christian theologian who was the founder of the (Evangelical) Armenian Methodist movement. "Methodism" was originally an unflattering nickname of the "Holy Club" at Oxford University founded by Charles Wesley but led by brother John. Methodism was well advanced in England through George Whitefield who had taken over the responsibility of the Holy Club while the Wesley brothers were in Savannah, Georgia.
On John Wesley's return to England in 1737 he publicly criticised Whitefield for his evangelical preaching. After John's Aldersgate experience in which he felt his heart "strangely warmed", he adopted what was to become known as "Arminian Evangelical Methodism" (John Fletcher of Madelay's later description). The Wesley Methodist Movement began when John Wesley was asked to take over the open-air preaching started by George Whitefield at Hanham Mount, Kingswood, Bristol, U.K.
Methodism was effectively divided into Arminian and Calvinistic groupings when George Whitefield departed for a second time in 1739 to Savannah to found the Bethleham Orphanage.
Wesley, along with others (Hywel Haris, John Cennick), continued Whitefield's work and practices with Wesley forming religious societies for the care of believers.
Methodism in both forms was a very successful evangelical movement in the United Kingdom. Wesley was a brilliant organiser and formed societies throughout England, Scotland, Wales, and Ireland. He divided his religious societies further into classes and bands for intensive accountability and religious instruction. His great contribution was to appoint itinerating (unordained) preachers who travelled widely to evangelise and care for societies.
Methodists, under Wesley's direction, became leaders in many social justice issues of the day including prison reform and abolitionism movements. Wesley's contribution as a theologian was to propose a system of opposing theological stances. His greatest theological achievement was his promotion of what he termed "Christian Perfection," or holiness of heart and life. Wesley insisted that in this life, the Christian could come to a state where the love of God, or perfect love, reigned supreme in one's heart. His evangelical theology, especially his understanding of Christian perfection, was firmly grounded in his sacramental theology. He continually insisted on the general use of the means of grace (prayer, Scripture, meditation, Holy Communion, etc.) as the means by which God transformed the believer.
Throughout his life, Wesley remained within the Church of England and insisted that his movement was well within the bounds of the Anglican Church. His maverick use of church policy put him at odds with many within the Church of England, though toward the end of his life he was widely respected.