I came across the following quote many years ago, and quite by accident. It is from a passage where Thomas Aquinas discusses the details of the Last Judgement. I was surprised by how close this is to the Wesleyan doctrine of Christian Perfection.
It seems to me that two prior traditions are meeting in this quote: one that affirmed the life of full dedication to God’s Purpose (early Greek Fathers?) and the other (Augustinian?) that affirmed that we could never be without sin. And Thomas attempts to somehow affirm both streams of tradition.
Among the good there are some who have wholeheartedly despised temporal possessions and have dedicated themselves to God alone and to the things that are of God. Accordingly, since sin is committed by cleaving to changeable goods in contempt of the changeless Good, such souls exhibit no mingling of good and evil. This is not to imply that they live without sin, for in their person is asserted what we read in 1 John 1:8: ‘If we say we have no sin, we deceive ourselves.’ although certain lesser sins are found in them, these are, so to speak, consumed by the fire of charity, and so seem to be nothing. At the Judgement, therefore, such souls will not be judged by an investigation of their deeds.
— Thomas Aquinas, Aquinas’ Shorter Summa: St. Thomas Aquinas’s Own Concise Version of His Summa Theologica (trans. Cyril Vollert) Sophia Institute Press: Manchester, New Hampshire 1993. p. 323.
What I don’t know is how this point of view may have influenced ideas in the teachings of St. John of the Cross or the other subsequent Christian mystic writers.