romans 12:2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God. - Free Bible Online

      2. And be ye not conformed to this world--Compare Eph 2:2; Ga 1:4, Greek.
      but be ye transformed--or, "transfigured" (as in Mt 17:2; and 2Co 3:18, Greek).
      by the renewing of your mind--not by a mere outward disconformity to the ungodly world, many of whose actions in themselves may be virtuous and praiseworthy; but by such an inward spiritual transformation as makes the whole life new--new in its motives and ends, even where the actions differ in nothing from those of the world--new, considered as a whole, and in such a sense as to be wholly unattainable save through the constraining power of the love of Christ.
      that ye may prove--that is, experimentally. (On the word "experience" see on Ro 5:4, and compare 1Th 5:10, where the sentiment is the same).
      what is that--"the"
      good and acceptable--"well-pleasing"
      and perfect, will of God--We prefer this rendering (with CALVIN) to that which many able critics [THOLUCK, MEYER, DE WETTE, FRITZSCHE, PHILIPPI, ALFORD, HODGE] adopt--"that ye may prove," or "discern the will of God, [even] what is good, and acceptable, and perfect." God's will is "good," as it demands only what is essentially and unchangeably good (Ro 7:10); it is "well pleasing," in contrast with all that is arbitrary, as demanding only what God has eternal complacency in (compare Mic 6:8, with Jer 9:24); and it is "perfect," as it required nothing else than the perfection of God's reasonable creature, who, in proportion as he attains to it, reflects God's own perfection. Such then is the great general duty of the redeemed--SELF-CONSECRATION, in our whole spirit and soul and body to Him who hath called us into the fellowship of His Son Jesus Christ. Next follow specific duties, chiefly social; beginning with Humility, the chiefest of all the graces--but here with special reference to spiritual gifts.

JFB.