That unchangeable feature of the Nature of God – his unyielding sanctity – is the basic fact of the Universe and therefore of our own lives in his sight.  God can never come to terms with evil in any shape, and when he meets it there is conflict.

An example of this is to be found in that strange, supernatural struggle when “war broke out in heaven; Michael and his angels fought against the dragon.  The dragon and his angels fought back, but they were defeated, and there was no longer any place for them in heaven” (NRSV, Revelation 12:7,8).

And there was conflict again when God the Son came into the world and confronted Satan on his own ground – on the hill of Calvary.

Nor, being God, can he overlook, still less condone, even the faintest shadow of sin in ourselves.  And when he meets Satan in our own souls that same conflict breaks out and discloses itself to us as the familiar struggle between conscience and temptation.  When conscience wins, we have thrust out Satan: when temptation wins, we have thrust out God.

For that reason perfection can be attained only by faithfully and persistently resisting those evil promptings which seek to deface the image of God in our souls.  As St Peter puts it, “Discipline yourselves; keep alert.  Like a roaring lion your adversary the devil prowls around, looking for someone to devour.  Resist him, steadfast in your faith…” (NRSV, 1 Peter 5:8,9).