Union with Christ, Andrew Purves argues in his book, The Crucifixion of Ministry, is “a key doctrine for practical theology and the faithful practice of ministry” (100). How does union with Christ work out for ministry?

Purves draws here on a sermon his wife, Cathy, preached. Rooted in Phil 3:12-14 (“I press on…”) she speaks of the famous book many of us read as kids and read to our kids, The Little Engine That Could. It’s the Protestant Work Ethic story.
But what Paul wants here is to know Christ, to run behind Christ, Christ crossing the finish line … it is about Christ doing for us.
If Christ’s humanity is vicarious, then our need is simply to be in union with the Big Engine That Did (that’s my play on Cathy’s image). It is about participation, not imitation.
Galatians 2:20 (“not I but Christ”) teaches the same. Union with Christ is the whole. Then Galatians 4:6 that God sent his Son and the Spirit. And then to John 15:1-11 that we abide in Christ.
Union leads to transformation of mind, conversion of the will, and amendment of life,.