J. B. Lightfoot on Colossians 2:18-19

ὑπὸ τοῦ νοὸς τῆς σαρκὸς αὐτοῦ, ^{19}καὶ οὐ εἰκῇ φυσιούμενος] ‘_vainly puffed up_.’ Their profession of humility was a cloke for excessive pride: for, as St Paul says elsewhere (1 Cor. viii. 1), ἡ γνῶσις φυσιοῖ. It may be questioned whether εἰκῇ should be connected with the preceding or the following words. Its usual position in St Paul, before the words which it qualifies (Rom. xiii. 4, 1 Cor. xv. 2, Gal. iv. 11; there is an exceptional reason for the exceptional position in Gal. iii. 4), points to the latter construction. τοῦ νοὸς κ.τ.λ.] ‘_the mind of his flesh_’, i.e. unenlightened by the Spirit; comp. Rom. viii. 7 τὸ φρόνημα τῆς σαρκός. It would seem that the Apostle is here taking up some watchword of the false teachers. They doubtless boasted that they were directed ὑπὸ τοῦ νόος. Yes, he answers, but it is ὁ νοῦς τῆς σαρκὸς ὑμῶν. Compare Rev. ii. 24, where the favourite Gnostic boast γινώσκειν τὰ βαθέα is characterized by the addition of τοῦ Σατανᾶ (see _Galatians_ p. 298 note 3). Comp. August. _Conf._ x. 67 ‘Quem invenirem qui me reconciliaret tibi? Ambiendum mihi fuit ad angelos? Qua prece? quibus sacramentis? Multi conantes ad te redire, neque per se ipsos valentes, sicut audio, tentaverunt hæc et inciderunt in desiderium curiosarum visionum et digni habiti sunt illusionibus. Elati enim te quærebant doctrinæ fastu, etc.’ 19. οὐ κρατῶν] ‘_not holding fast_.’ This is the most common construction and meaning of κρατεῖν in the New Testament; e.g. Mark vii. 8 _ἀφέντες_ τὴν ἐντολὴν τοῦ Θεοῦ _κρατεῖτε_ τὴν παράδοσιν τῶν ἀνθρώπων; comp. Cant. iii. 4 ἑῦρον ὃν ἠγάπησεν ἡ ψυχή μου, ἐκράτησα αὐτὸν καὶ οὐκ ἀφῆκα αὐτόν.