In 1 Samuel, when God is directing Samuel to anoint David king, Samuel first sees David's brother Eliab and thinks that surely he is the one to be king. God's response is a text from which Wesleyans have often preached: "Do not look on his appearance or on the height of his stature, because I have rejected him; for the Lord does not see as mortals see; they look on the outward appearance, but the Lord looks on the heart" (1 Sam. 16:7, NRSV). People look at outward appearance; God looks at the heart.
The Wesleyan tradition is not primarily oriented around what we as Christians believe, although beliefs are important. Actions are also very important to our tradition, but even here, the Wesleyan tradition at its best is not primarily focused on behavior. At its best, the Wesleyan tradition is focused on the heart rather than the head or the hands.
And rightly so. Jesus himself in Mark 7 affirms this heart orientation when he rejects a focus on Levitical purity in deference to the attitude of the heart (Mark 7:20-23). We also misunderstand Paul if we think his sense of God's standard of righteousness is really absolute. We do not rightly understand Paul if we think his definition of sin is anything short of absolute perfection. Sin for him is "whatever does not proceed from faith" (Rom. 14:23). In other words, sin is primarily a matter of intention rather than performance. 
John Wesley did not start out intending to found a church. In fact, he remained an Anglican minister till his death, even though he did ordain bishops for the newly formed United States of America. When he gave the "Methodist" movement clarity on what to believe, he did not write a "systematic theology," as John Calvin had two hundred years before. Instead, he bequeathed his followers a set of standard sermons. If this movement of lay leaders and Anglican ministers would preach in agreement with those sermons, then they were part of the movement.
Some might want to think less of these Methodists for such a practical orientation. Wesley himself ironically had the personality of a purist, an idealist. But his ideas also told him that the mission trumped his preferences. So Wesley no doubt hated preaching outside church walls, something that simply was not done in his day. His personality was such that he no doubt hated breaking this long standing understanding of where worship takes place. But when he did not have a pulpit available, he did the next best thing. He made an exception.
This is the ethos of the Wesleyan tradition, and we believe it flows nicely from Scripture. Notice the difference in emphasis from that of some other Christians today. One hears a lot today about how important absolutes are. But the nature of absolutes is not to make exceptions. Such was not Jesus' orientation, who was criticized for the exceptions he made. Such was not the nature of Wesley, who compromised on non-essentials so that the essentials could take place. Such rhetoric is foreign to the Wesleyan tradition, that wants to bring God's will to bear on this particular situation, not to force some supposed exceptionless rule on every situation...
 To be sure, one can also wrong another person unintentionally and a person can be unaware of sinful motives. But the starting point for understanding sin is with intent.