John Wesley claimed to be “a man of one book.” Nevertheless, his system of thought, which became Methodism, was clearly molded by extra-biblical influences. Murray names these as “High Church divinity, Christian mysticism, and Moravian evangelicalism,” and adds, “It would be a mistake to suppose that the influence of the first two ended when he embraced the third.”

   High church thinking remained with him in more than one area. On baptism, for instance, he continued to believe that a decisive change occurs when a child receives the sacrament. Before that event original sin operates in its full power in all the sons of Adam, but in baptism the merit of Christ’s death begins to be applied to all and there is a general giving of the Holy Spirit sufficient to enable a response to the gospel. This was his teaching on ‘prevenient grace’. He also believed that the Lord’s Supper could be viewed as a means of conversion. His ‘High’ beliefs about the sacraments likewise may have entered into his readiness to allow unordained preachers to expound Scripture, whereas they were not to baptize or to administer the Lord’s Supper.
   From this same High Church came what can only be called a form of ‘asceticism’ which remained in Wesley’s thinking. High Church and mystical writers majored on self-denial. Certainly, self-denial is a Christian duty, and it was to contribute largely to the spirituality and vigour which would characterize Methodists. In Wesley, however, it could pass into asceticism, not simply in such things as early rising and abstinence from tea-drinking but, more seriously, in his whole view of marriage. To a young preacher who nearly fell into matrimony he could write, ‘I congratulate you on your deliverance . . . remember the wise direction of à Kempis, “Avoid good women, and commend them to God.”’ . . . [Wesley’s own] marriage was a disaster. This might have been the case whoever he had married, given his estimation that celibacy remained a higher state, and that marrying for happiness was somehow beneath a Christian: ‘I married because I needed a home’, he tells a correspondent, ‘in order to recover my health; and I did recover it. But I did not seek happiness thereby, and I did not find it.’ Who can be surprised?
   . . .
   Asceticism is not a charge which Wesley would have recognized, but there was another strand in his thinking that he willingly attributed to his early reading of High Church authors and the mystics. This was his teaching on ‘Christian perfection’ . . . in its final form his teaching, in brief, was that the mature or ‘perfect’ Christian . . . can attain to loving God with heart and soul and strength before death, and so overcome all inbred sin that sinning may be said to have ceased. To describe this attainment he used several terms, ‘full sanctification’, ‘pure love’, ‘Christian perfection’, and less commonly, the ‘second blessing’. This condition might be received by faith in an instant. ‘Full deliverance from sin, I believe, is always instantaneous.’ . . .
   . . . it is no conjecture to believe that Wesley’s ‘evidence’ for the opinion rested quite as much upon alleged experiences as upon any interpretation of Scripture . . . although Wesley criticized the mystic writers with the words, ‘each of them makes his own experience the standard of religion’, a propensity to depend on experience as a guide to truth also remained with him. For example, to support his assertion, given above, that full deliverance from sin, I believe, is always instantaneous’, he adds, ‘at least, I never yet knew an exception.’

—Iain Murray, Wesley and Men Who Followed (Banner of Truth, 2003), 44–48.