<p>4:17 <i>Therefore, this I say and testify in the Lord: You are to no longer walk as the Gentiles walk, in the vanity of their mind</i>- Paul reminds them that his teaching here is a direct testimony from the Lord Jesus. A new section of practical advice now follows. The way of the flesh, be it wanton immorality or simply living in the vanity of the mind, is not as the Ephesians had been taught the Gospel of Christ before their baptisms. That basic Gospel had very practical implications (Eph. 4:17-27). And more than this. The new wine of the Gospel will destroy a man who holds it unless he changes his life (cp. the wine skin), so that it too is new. The new cloth of the Gospel will rip a man apart who doesn't change from his old clothing. Leaven is an apt symbol of the Gospel, in that it corrupts terribly <i>if it is left idle</i>. If the principles of the Truth lie dormant in our lives, they can only destroy us. The idea of 'walking' connects with the opening charge of :1, that we are to walk in a way appropriate to our calling. &quot;The mind&quot; is Biblically called &quot;the spirit&quot;. Unbelievers think in vanity, and we catch ourselves spending large amounts of mental time imagining or chattering within ourselves about vain things. How we think in the mind is how we walk in practice. The receipt of God's Spirit into our spirit will therefore issue in a quite different walk. Vain thinking is a particular malaise of our online world. The inane and meaningless have been glorified.</p>