Open-air preaching was resorted to by George Whitefield in 1739 as a means of reaching the Kingswood miners and other unchurched people in the Bristol area. Despite Whitefield's considearble success, the Wesley brothers had serious reservations because of its past association with Dissent and political disaffection. But on April 2, 1739, John Wesley 'submitted to be more vile' and, encouraged by the precedent of the Sermon on the Mount, took over Whitefield's open-air witness in Bristol. By the end of May Charles Wesley too had overcome his misgivings and field preaching became a major element in the Methodist revival, provoking charges of breaking the Conventicle Act.
Wesley later gave as his main reason for preaching 'abroad' his exclusion from the parish churches, or the inadequacy of other buildings to contain the congregation. According to his Journal, his method of calculating the size of his open-air congregations was the formula of five people to one square yard.
Wesley developed techniques for making himself audible to great numbers. At the 1747 Conference, he declared that it enabled the Methodist preachers to reach many who would never enter a church, but admitted that, while it aroused popular curiosity, it 'rarely made any impression at all till the novelty of it was over'. He had already found, especially in Wales and Cornwall, that preaching not followed up by forming societies was ineffective.
Wesley confessed in 1759 that he persisted in open-air preaching in spite of his preference for the ease and comfort of an indoor pulpit. He himself preached his last open-air sermon in Winchelsea at the age of 87, on October 7, 1790. After 1800 some WM itinerants gave up open air services in areas where they had large chapels, but in new areas especially many continued to hold services outside for mission purposes. The tradition was otherwise left to the early PM and BC preachers. Its twentieth century equivalent is the 'ministry of controversy' exemplified by the open-air witness of Lord Soper.
John Wesley's Journal:
Saturday, 31 March 1739: 'In the evening I reached Bristol, and met Mr. Whitefield there. I could scarce reconcile myself at first to this strange way of preaching in the fields, of which he set me an example on Sunday; having been all my life (till very lately) so tenacious of every point relating to decency and order, that I should have thought the saving of souls almost a sin if it had not been done in a church.' Sunday 1 April: 'In the evening, Mr. Whitefield being gone, I began expounding our Lord's Sermon on the Mount (one pretty remarkable precedent of field-preaching, though I suppose there were churches at that time also) to a little society which was accustomed to meet once or twice a week in Nicholas Street.' Monday 2: 'At four in the afternoon I submitted to be more vile [2 Samuel 6:22] and proclaimed in the highways the glad tidings of salvation, speaking from a little eminence in a ground adjoining to the city, to about three thousand people. The scripture on which I spoke was this (is it possible any one should be ignorant that it is fulfilled in every true minister of Christ?), "The Spirit of the Lord is upon Me, because he hath anointed Me to preach the gospel to the poor. He hath sent Me to heal the broken-hearted; to preach deliverance to the captives, and recovery of sight to the blind; to set at liberty them that are bruised, to proclaim the acceptable year of the Lord." '
4 June 1739: 'Many came to me and earnestly advised me "not to preach abroad in the afternoon, because there was a combination of several persons who threatened terrible things". This report being spread abroad … added, I believe, more than a thousand to the ordinary congregation… The power of God came with his Word, so that none scoffed or interrupted, or opened his mouth.'
Charles Wesley's Journal:
29 May 1739: ' Franklyn, a farmer, invited me to preach in his field. I did so, to about five hundred, on "Repent, for the kingdom of heaven is at hand" I returned to the house rejoicing.'
John Wesley's Journal:
25 June 1759: 'On Monday and Tuesday evening, I preached abroad near the Keelmen's Hospital [Newcastle upon Tyne] to twice the people we should have had at the house. What marvel the devil does not love field-preaching? Neither do I - I love a commodious room, a soft cushion, an handsome pulpit. But where is my zeal if I do not trample all these under foot, in order to save one more soul?'