"15 Look carefully then how you walk, not as unwise but as wise, 16 making the best use of the time, because the days are evil. 17 Therefore do not be foolish, but understand what the will of the Lord is. 18 And do not get drunk with wine, for that is debauchery, but be filled with the Spirit, 19 addressing one another in psalms and hymns and spiritual songs, singing and making melody to the Lord with your heart, 20 giving thanks always and for everything to God the Father in the name of our Lord Jesus Christ, 21 submitting to one another out of reverence for Christ."
The same wisdom must be 'read into' our walking in the light, into our 'holiness'. Be wise, says the Apostle, in your holiness, not hard or forbidding, but tender and understanding and compassionate. Do not 'slap people down' in asperity and with a frown; there is all the difference in the world between a cold, disapproving look that reminds one of a moral disinfectant as much as anything and the attitude of our Lord in His treatment of the woman taken in adultery, when He said to her, 'Neither do I condemn thee: go and sin no more'. Which attitude do we suppose would be more likely to make the woman want to go out to live a different kind of life - the asperity, or the compassion?
We should note the link between 'redeeming the time' in 16 and 'understanding what the will of the Lord is' in 17. The implication seems to be that we can sometimes waste a great deal of time trying to decide what God's will is for our lives. It is safe to say that almost no issue is so perplexing and beset with difficulties - both for young believers and also for those not so young - as knowing the will of God for their lives. The fact that Paul speaks of walking circumspectly, and in wisdom, is an indication as to how to discern the divine will. We are to seek to understand what that will is. One of the lessons this teaches is that there is a purposive will for our lives in the good providence of God. The AV phrase 'not as fools, but as wise' is translated by J.B. Phillips as 'not as men who do not know the meaning and purpose of life, but as those who do'. This is a very perceptive rendering, and what it stresses is the need to have a sense of direction, and have the wisdom and grace to follow it. The key word, of course, is 'understanding' what that will is, and if it is something that can be understood, we must apply our minds to it and think things through. This is so important that we must spend another day considering it more fully.