Imagination is simply the ability to think of something that is not there. It can be a truthful imagination in the sense that it could actually exist or happen, such picturing in my mind how my walls would look in a different color. It can also be fictional imagination, such as elves cooking my supper.
God wants me to set my imagination on Him. This is not easy. He is a Spirit so cannot be seen or even described, but He does give me the ability to sense His presence. He also revealed Himself in Jesus Christ, so by the New Testament narratives, I can imagine a man who heals the sick, raises the dead, and loves me unconditionally, although this latter one is difficult at times.
He also wants me to imagine what He has done and can do. Looking at creation helps me do that. Focusing on answers to prayer or the changed lives of other Christians is also helpful, even though the main source for my imaginative thoughts is the Word of God where I can read about what He has done and has promised. Yet there is far more to God than what has been recorded even in the Bible. This verse of benediction hints it:
Now to him who is able to do far more abundantly than all that we ask or think (imagine), according to the power at work within us, to him be glory in the church and in Christ Jesus throughout all generations, forever and ever. Amen. (Ephesians 3:20–21)
God is able to do more than I can ask or imagine. No one can second-guessed Him or know for certain what He is going to do, even in answer to prayer. He is full of surprises. He says His thoughts are beyond my thoughts. At the same time, He tells me to have a mind that is changed, that leans toward His thoughts, His will, His ideas.
Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect. (Romans 12:2)
In renewing my mind, I must turn from the old stuff. That is, whatever held my imagination before I became a Christian has to be put off, discarded, and rejected. I’ve been given a new way to think, even given the mind of Christ (1 Corinthians 2:16). For this reason, God tells me to abandon the thoughts of those who do not know Him and whose minds cannot grasp the life of God because their hearts are hard. Their thoughts are “sensual, greedy . . . and impure.”
He tells me that is not the way that I learned Christ — assuming that I have heard about Him and have been taught in him. As the truth is in Jesus, I am to put off my old self which belongs to my former manner of life which is corrupt through deceitful desires, and be renewed in the spirit of my mind, putting on the new self which has been created after the likeness of God in true righteousness and holiness. (Ephesians 4:20–24)
I am to set my mind on things that are above, not on things that are on earth. He says, “For you have died, and your life is hidden with Christ in God. When Christ who is your life appears, then you also will appear with him in glory.” (Colossians 3:2–4)
Another helpful way to keep my imagination where it should be is to trust God instead of anything else, including my ideas and imagination. Trust is key to being at peace . . .
You keep him in perfect peace whose mind is stayed on you, because he trusts in you. (Isaiah 26:3)
An added thought from Chambers is that an imagination that is not fixed on God in trust will produce exhaustion. Of course, hard work will do the same, but waiting on God renews my strength and overcomes fatigue and weakness, another good reason to “bring every thought into captivity to the obedience of Christ.”
A rich and godly imagination will not only keep me filled with spiritual energy, but also deepens my affection for God and keeps my heart settled in perfect peace.