The Gospel as preached by Wesley and those who imitate him, appeals with peculiar force to the intelligent common-sense of all unconverted men. All such men feel that under the circumstances and conditions of human life, it was incumbent upon God to make salvation possible to every soul. It has been the mission of Methodism to destroy the unreasonable and illogical and unscriptural dogmas of Calvinistic fatalism, and show how God could be just and yet the justifier of every believing soul that in real penitence accepts the Lord Jesus Christ; and, also, how God can save all infants and irresponsible persons, and how in every nation all who fear God and work righteousness, though they have never heard the Gospel, are accepted by Him. These fundamental truths as set forth by John Wesley, have never failed to commend themselves to the favorable consideration of all unprejudiced minds, for they at once glorify the Divine justice and compassion, and throw wide open the door of hope to every soul. But Wesley was thorough and exhaustive in his treatment of whatever was the subject of his investigations. For many long and weary years he groped in the thick darkness of the times in which he lived, seeking for the simplest experience of salvation. He abounded in all manner of self-denials and self-sacrifices; his morality was [of] the most exalted character; he was diligent in prayer and in the study of God's word; he was most strict in all the outward forms and services of religion; but until he reached his thirty-fifth year he had not attained the consciousness of pardon in his own soul; he could not testify that God for Christ's sake had forgiven him his sins. From that auspicious and ever-memorable, as well as glorious hour, when, listening to the reading of Luther's Preface to the Epistle to the Romans, he felt his heart strangely warmed with the love of God, and knew himself to be a pardoned sinner, he went straight forward as the Spirit of God directed his steps, till he came to the experience of perfect love in his own soul.
— from the Introduction to Christian Perfection as Taught by John Wesley complied by J. A. Wood.
Also found here: Why I Still Find Wesleyan Theology Interesting.