Be not conformed... but be ye transformed. — Here the English is somewhat misleading. It would naturally lead us to expect a similar play upon words in the Greek. But it is not so; indeed, there is a clear distinction between the two different words employed. It is the difference between an outward conformity or disguise and a thorough inward assimilation. The Christian is not to copy the fleeting fashions of the present time, but to be wholly transfigured in view of that higher mode of existence, in strict accordance with God’s will, that he has chosen.
This world. — Not here the same word as that which is used, e.g., in 1 John 2:15-17, but another, which signifies rather the state of the world as it existed at the Coming of Christ, as opposed to the newly-inaugurated Messianic reign. “To be conformed to this world” is to act as other men do, heathen who know not God; in opposition to this the Apostle exhorts his readers to undergo that total change which will bring them more into accordance with the will of God.
By the renewing of your mind. — “The mind” (i.e., the mental faculties, reason, or understanding) is in itself neutral. When informed by an evil principle, it becomes an instrument of evil; when informed by the Spirit, it is an instrument of good. It performs the process of discrimination between good and evil, and so supplies the data to conscience. “The mind” here is not strictly identical with what we now mean by “conscience;” it is, as it were, the rational part of conscience, to which the moral quality needs to be superadded. The “renewed mind,” or the mind acting under the influence of the Spirit, comes very near to “conscience” in the sense in which the word is used by Bishop Butler.
Prove. — As elsewhere, “discriminate, and so approve.” The double process is included: first, of deciding what the will of God is; and, secondly, of choosing and acting upon it.
What is that good, and acceptable, and perfect, will of God. — The “will of God” is here, not the divine attribute of will, but the thing willed by God, the right course of action. Are we to take the adjectives “good, and acceptable, and perfect” (with the Authorised version), as in agreement with this phrase, or are they rather in apposition to it, “that we may prove the will of God, that which is good, and acceptable, and perfect”? Most of the commentators prefer this latter way of taking the passage, but it is not quite clear that the former is impossible, “that good, and acceptable, and perfect thing, or course of action which God wills.” “Acceptable,” that is to say, to God Himself.