There are two parts of conversion, answering to two ends. For the person who is converted is converted from bad to good, from darkness to light, from the slavery of Satan to God (1 Ki. 8:25; Is. 59:20; Jer. 15:19; Acts 26:18).
These parts are called in Scripture nekrosis, mortification, or ekdosis, the putting off of the old man; and zoopoiesis, vivification and endusis, the putting on of the new man. ‘Having put off the old man with his deeds; and having pit on the new man, which is renewed in knowledge after the image of him that created him’ (Col. 3:9-10, see also Eph. 4:22-24 and Gal. 5:24-25).
These parts go together. But, as regards the order of nature, although newness be subsequent to oldness, […] yet the newness of the love of God is the cause of abolishing the oldness of the enmity of God. Darkness is not removed except by light; nor death except by life; nor poverty except by riches; nor nakedness except by being clothed; nor ugliness except by beauty; nor vice except by virtue; in the same way, neither is hate except by love.
– Johannes Cocceius (1603-1669), Summa Theologiae, XLV. 6-8.