"And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God."  Romans 12:2

"Try it … you'll like it."  As a pre-schooler I remember my mother trying to get me to taste apple juice.  It just didn't look right to me.  Having two older brothers, you can imagine I was gun-shy at "trying" things.  Even my mom might be pulling a fast one.  A little guy can't be too careful. …  I was sure it was vinegar and she was getting ready for a big laugh at my expense. …  But it was really apple juice.  I tried it, and of course it was very tasty to a young palate.

I'm known as an amateur connoisseur of good, hole-in-the-wall eating places.  When people are going out of town, they'll ask me a spot to eat and generally I can tell them where to go.  I get to travel a lot, and when I go to an unfamiliar town, I always ask the locals for the best places.  However, I wouldn't know if they were really good unless I tried them for myself. 

There is no way you are ever going to experience personally how wonderful, how good and well-pleasing and perfect God's will is until you:  a) Know what it is, and b) try it for yourself. 

Paul wants us to be transformed by the renewing of our minds so that we can experience how wonderful doing God's will is.  To prove (dokimazo – to approve, test, try, find out) in this case has the idea of finding out and substantiating by personal experience.  You won't taste how good God's will is until you do it; you won't do it until you know what it is; you won't know what it is until you renew your mind

How do we renew our minds?  The noun (anakainosis) is only used here and Titus 3:5, "according to his mercy He saved us, through the washing of regeneration and renewing of the Holy Spirit."  The verb is only used two other times, 2 Corinthians 4:16, "Therefore we do not lose heart.  Even though the outward man is perishing, yet the inward man is being renewed in knowledge according to the image of Him who created him."

Some clues for renewing our minds are these:  The renewing is something the Holy Spirit does (Titus 3:5).  An outside (A)gent is also implied in the other two verses where "being renewed," or "is renewed," are both in the passive voice.  In other words the inward man, or new man, is not renewing himself (which would require the Greek middle voice), but something or someone outside of him is doing the renewing.  Nevertheless, living according to the Spirit does not mean we are passive (8:1-17).  As mentioned, it requires our willpower and having a spiritual mindset (see Walking According to the Spirit).  Our part in "renewing" our minds would include the Spirit-aided obedience of thinking "on the things of the Spirit" which will include attention to the lifestyle commands which follow (the rest of Romans, 12:3ff.), and ultimately all the Scriptures.

The command "be transformed" concurs with this.  The word metamorphoo, the word from which we derive metamorphosis, is only used four times in the New Testament.  Twice in reference to the transfiguration (Mt. 17:2; Mk 9:2), and illustration of the transformation we will experience when we get our glorified bodies.

The only other reference sheds great light on our passage here.  The metamorphosis of which 2 Corinthians 3:18 speaks is the process of healthy Christian growth, from one stage to the next, which the Holy Spirit produces in us, transforming us to the image of Christ.  We have a vital part in that growth Paul says, "But we all, with unveiled face (he has already explained, that in contrast to the Jew whose heart is still "veiled" in unbelief, the veil is "taken away in Christ" for the believer), beholding as in a mirror the glory of the Lord, are being transformed into the same image from one stage of glory to the next, just as by the Spirit of the Lord" (2 Cor 3:18).  The miraculous mirror in which we see the image of the glory of the Lord – Jesus Christ (see 2 Cor 4:4) – and into which we are transformed by the Spirit's transforming work, is none other than the mirror of God's Word spoken of in James 1:21-25.