We Are to Be Sound in Mind
Romans 12:3 Updated American Standard Version (UASV)
3 For through the grace given to me I say to everyone among you not to think more highly of himself than he ought to think; but to think so as to have a sound mind, each one as God has apportioned to him a measure of faith.
Sound in Mind: (Gr. sophroneo) This means to be of sound mind or in one’s right mind, i.e., to have understanding about practical matters and thus be able to act sensibly, ‘to have sound judgment, to be sensible, to use good sense, sound judgment.’–Acts 26:25; Romans 12:3; 2 Timothy 1:7; Titus 2:6; 1 Peter 4:7.
Sober Minded: (Gr. nepho) This denotes being sound in mind, to be in control of one’s thought processes and thus not be in danger of irrational thinking, ‘to be sober-minded, to be well composed in mind.’–1 Thessalonians 5:6, 8; 2 Timothy 4:5; 1 Peter 1:13; 4:7; 5:8.
Being “sound in mind” does not mean that have been educated in the universities of this world. God said, “I will destroy the wisdom of the wise, and the discernment of the discerning I will thwart.” (1 Cor. 1:19) Being sound in mind means that we need ‘to be renewed in the spirit of our minds.’ (Eph. 4:23) “How? You are what you think. You move in the direction of what you put into your mind and what you allow your mind to dwell on.” Being sound in mind implies that we are aware of our spiritual needs, and we are taking steps toward becoming and remaining spiritually healthy. (Tit. 2:2; Jer. 3:15)
What does it mean to be “sound in mind”? In view of Christ’s return, where should the Christian mind be focused? The Greek word nepho, for “sound in mind” is rendered as follows by other translations: “sober-minded” (English Standard Version), “remain calm” (The New American Bible), “sane” (Revised Standard Version), “be of sound judgment” (New American Standard). Paul also uses the same Greek word under a similar context, when he writes, “So then let us not sleep, as others do, but let us keep awake and be sober.” (1 Thess. 5:6, ESV) Other translations have “be self-controlled” (LEB), and “be serious” (HCSB). The sense of the word is that we need to ‘keep our senses.’ However, in relation to what should we be sober-minded, serious-minded, sound in mind, possessing self-control, using sound judgment, keeping our senses?
The Christians who walked with Jesus, who witnessed his execution, and his resurrection, as well as his ascension, were very alert for his return decade after decade. Even thirty years after Jesus ascension, Peter is telling the people “the end of all things is at hand.” Peter did not tire of waiting, nor did he stop believing as though it were imminent. This is when he offers the critical advice to “be sound in mind.”
The Greek nepho, “sound in mind” is literally “sober-minded.” In other words, it means to think properly. Yes, figuratively, it means to “be free from every form of mental and spiritual ‘drunkenness.” This is not literal drunkenness, but rather any irrational thinking, which may give you the wrong perception. This is sort of a spiritual clear-headedness when it comes to our worship of God. If we are thinking correctly, we will better understand, perceive what the will and purposes of God are, and then apply them accordingly. Reasonably, we walk by self-control and steadiness in sound thinking, our outlook, and behavior, in our seeking the kingdom of God.
Consequently, if we are “sound in mind,” we will not fall victim to Satan’s world that caters to the fleshly desires. If we are “sound in mind,” we will “flee from sexual immorality.” (1 Cor. 6:18) If we are “sound in mind,” we will “seek first the kingdom of God and his righteousness.” (Matt. 6:33) This soundness of mind will strengthen us against anything that might jeopardize our relationship with God.
 William Arndt, Frederick W. Danker and Walter Bauer, A Greek-English Lexicon of the New Testament and Other Early Christian Literature, 3rd ed., 672 (Chicago: University of Chicago Press, 2000).