What exactly is perfection, anyway?

Since love and relationship were now at the heart of his understanding of salvation, he was beginning to distinguish between perfect intention and perfect performance. The latter was the concern of those who upheld the centrality of perfect obedience to God’s law; the former was related to the essential nature of a relationship based on love. In a relationship of love, there can be pure intention (a matter of the heart) but flawed performance (due to a corruptible mind and body). Because of intention, the essential nature of sin was seen as a deliberate and willful choice to harm the relationship; thus its ‘voluntariness’ was a crucial part of his definition of terms.—Wesley as a Pastoral Theologian, page 57

<idle musing>
"Because of intention, the essential nature of sin was seen as a deliberate and willful choice to harm the relationship." That's the core, right there. Sin is not so much activity, but the intention behind it. The intention is what causes the action.

I've heard some people define sin in such a way that humanity was sinful even before the fall! I wonder about their understanding of the incarnation in those cases. If existing as a physical being is sinful, then the incarnation didn't really happen—they call the docetism (Jesus just appears to be human, from Greek δοκέω/dokew, to seem) and the church denounced it as a heresy many a long year ago...
</idle musing>