1 Corinthians 3:18,19

‘Let no man deceive himself. If any man thinks that he is wise among you in this world (or ‘age'), let him become a fool that he may become wise. For the wisdom of this world is foolishness with God.'

Paul comes back to what has been his theme all along. The need to recognise the wisdom of God, that is, to recognise in Christ crucified the wisdom of God which must be central in all they teach (1 Corinthians 1:30), and not to be taken up with the wisdom of the world. There is to be no doubt about it. They must not deceive themselves. The man who thinks himself wise must deliberately become a ‘fool' (moros) in the world's eyes and in the eyes of the times in which he lives, in order to become wise. He must recognise in the foolishness of the cross his central message. Then he will be truly wise. For otherwise the wisdom that he has will be foolishness in God's eyes.

‘If any man thinks.' Compare 1 Corinthians 8:2; 1 Corinthians 14:37. Men thinks so much of themselves. Well let them think truly. If they think they are wise, or knowledgeable, or spiritual, let them consider. Let them be sure that they are right.

For if a man tries to build up a reputation for wisdom in any other way than through God's wisdom (and how we love to be thought wise) let him remember that whatever men think of it, the wisdom of the world is foolishness with God. Paul is not of course denying the usefulness of practical knowledge, he is speaking of ‘wisdom' with regard to metaphysics and the things of God. Religion without the centrality of Christ the Crucified One is folly in God's eyes.

The word ‘fool' was used by Stoic and Cynic philosophers to describe those who showed no interest in philosophy. Paul turns the idea on themselves. He claims that they, and all who philosophise about God apart from Christ, are in fact such fools. That the real fool is actually the pagan philosopher, for he ignores God's message and God's ways now revealed in Christ.

‘This world.' The word is difficult of exact translation for it signifies both ‘this world' as against the world of heavenly minded people, and ‘this age' as prior to, and opposed to, the coming age when God will be all in all. But in both cases the emphasis is the same. ‘This world' is the world as it is over against the true God. It disregards God and is unaware of what He really is, and is basically antagonistic towards Him. ‘This age' is the same. It represents the ideas of those who live in an age which is prior to, inferior to and opposed to the age of God, taken up with the present, treating God casually, and disregarding of the future. But while the Christian lives in this world and in this age, he is not of this world and he is not of this age. His thoughts are on God and His ways. He obeys God rather than men (although recognising earthly authority as for the good of all). He already has and lives out ‘eternal life', the ‘life of the coming age' and his citizenship is in Heaven, where his thoughts are also fixed. He knows that he lives in the heavenlies (Ephesians 1:19 to Ephesians 2:6).