My favorite book of JI Packer’s is one I do not hear a lot about, Keep in Step with the Spirit. It is a significant contribution to understanding sanctification and the many nutty ideas that get us sidetracked. He is generous with the “deeper life” movements ensconced in the Pentecostal and Keswick traditions, but he does take them to task for views that just do not stand up to the Bible’s teaching and human experience. I grew up with the Higher Life movement and always felt uncomfortable with Watchman Nee and the teachings on sanctification flowing out of Columbia Bible College (and the English Keswick movement) that flowed into our church. They seemed to be, and are, the search for altered states of consciousness, as in talking myself into something that will reduce the pain of spiritual combat and relieve me of the duty of choice. This may work short term but the mental gymnastics it requires cannot be kept up. Requires too much smoke and mirrors.
The Puritan model of sanctification is my own and the one in which Packer has confidence. Sanctification is not an act of God but a work of God that requires my cooperation in making moral choices of my own free will. Some Pentecostal and Wesleyan traditions make sanctification an act, a one step act of God bringing the Christian to the higher life through a faith step by the believer. In other words, as we were saved through faith in justification so we are saved through faith in sanctification. I don’t see it taught in the Bible nor validated in experience. What it does do is bring a mental and spiritual malaise upon Christians as they search for the one key that will unlock the door to victory. Packer deals with this powerfully and puts it to bed.