One of the distinct emphases of Wesleyanism in general, and United Methodism in particular, is that of sanctifying grace. This is what we refer to as Christian holiness, or what Wesley termed 'Christian perfection.' As United Methodists we have several foundational documents for our beliefs and behaviors. These include our Articles of Religion, the General Rules, and Wesley's Sermons and Notes on the New Testament. To this end we hold core beliefs and values such as found in the Doctrinal Standards, Theological Task, and Social Principles. One of these distinct beliefs is the notion of Christian perfection. This is probably most clearly articulated in Wesley's sermon on the subject, and his work, "A Plain Account of Christian Perfection."
Christian Perfection as Wesley expounded and Methodists believe is rooted in the idea of sanctification. That is, when we become children of God we are made right (justified) and made new (sanctified) simultaneously. Thus, for the believer, Christian perfection is a clarion call from God, found in scripture, to grow in holiness/sanctification. This is because sanctification is both a crisis and a process. Wesley taught that in an instant we are regenerated and are dead to sin, and alive to God in Christ Jesus. Yet there is a lifelong process whereby we become more and more like Jesus (Rom. 8:29). So, Christian perfection is the act and process of becoming perfect, in order that every part of us loves God, and loves others as ourself, and our desire to sin is cleansed by the Holy Spirit.
Though many are upset by the term "Christian perfection" Wesley believed that he must preach the "whole counsel of God" (Sermon 40) especially on account that the doctrine was profusely found in scripture. "Indeed, [Christian perfection] is only another term for holiness." (Wesley) He also believed that those who are holy are perfect according to scripture (Sermon 40). Wesley, in his sermon on the topic, devotes his organization to understanding what Christian perfection is, and what it is not. Christians are not perfect in the sense of knowledge. We still remain ignorant in mysteries of the faith. Neither are Christians free from mistake. Christian perfection does not make us supernaturally competent. Neither does being perfect mean freedom from infirmities (morally neutral inward/outward imperfections, e.g. forgetfulness). In addition, Christian perfection is by no means a complete freedom from temptation or the ability to sin. The opportunity and possibility remain.
Yet Wesley is clear what constitutes Christian perfection. It is both inward and outward. It involves inner affections, motives, and desires (cf. Wesley's Notes on Gal. 2:20). This is what Wesley called freedom from "evil thoughts and tempers" (Sermon). It also involves specific actions, words, and behaviors. Wesley firmly believed that Christian perfection involved being made free from outward sin in the sense of not continuing in sin (habitually, continually, 1 John 3:8-9, 5:18; Rom. 6:1-2; However, if one does sin cf. 1 John 2:1). Christian perfection is both negatively and positively expressed (i.e. sinful nature destroyed and Christ's holy living presence in us). Wesley describes this beautiful perfection as a deliverance not only from outward sin, but also the inner sin of the heart. Wesley had an optimistic view of the human condition only because of God's sanctifying grace, and the abundance of evidence for Christian perfection found in scripture. He used language such as "being filled up to all the fullness of God" (Eph. 3:19) seeing Christian perfection as being full of God's "light, love, wisdom, holiness, power, and glory." (Wesley's Notes, Eph. 3:19). Furthermore, he noted the command in Matthew 5:48 "be perfect as your Father is perfect" as a wise and gracious promise of God to perfect the believer (Wesley's Notes, Matt. 5:48).
In summary, Christian perfection (holiness, maturity) is attained by faith through the work of the Holy Spirit in one's heart and life. It is received by the grace of God whereby the believer desires less and less to do wrong. It is lived by daily surrender to God, in covenant to live wholly for Him, and to use the means of grace to increase in love for God and others, renouncing the works of sin and death.