In scores of commentaries and introductions, it is customary to hear over and over that Paul wrote this letter in part to respond to false teachers in Colosse. "Teachers," plural; never singular, that I've seen. In A. T. Robertson's day, it was taken for granted that the false teachers were Gnostics. Don Carson says that Edwin Yamauchi's case against pre-Christian Gnosticism has never really been overturned.
But my focus is much tighter than the disputed nature of the Colossian heresy. Compare the following.
First, from Galatians, another church beset with false teaching:
1:7 ὃ οὐκ ἔστιν ἄλλο, εἰ μή τινές εἰσιν οἱ ταράσσοντες ὑμᾶς καὶ θέλοντες μεταστρέψαι τὸ εὐαγγέλιον τοῦ Χριστοῦ.Now, from Colossians:
5:10 ἐγὼ πέποιθα εἰς ὑμᾶς ἐν κυρίῳ ὅτι οὐδὲν ἄλλο φρονήσετε· ὁ δὲ ταράσσων ὑμᾶς βαστάσει τὸ κρίμα, ὅστις ἐὰν ᾖ.
5:12 Ὄφελον καὶ ἀποκόψονται οἱ ἀναστατοῦντες ὑμᾶς.
2:4 Τοῦτο λέγω, ἵνα μηδεὶς ὑμᾶς παραλογίζηται ἐν πιθανολογίᾳ.What do you notice?
2:8 Βλέπετε μή τις ὑμᾶς ἔσται ὁ συλαγωγῶν διὰ τῆς φιλοσοφίας καὶ κενῆς ἀπάτης κατὰ τὴν παράδοσιν τῶν ἀνθρώπων, κατὰ τὰ στοιχεῖα τοῦ κόσμου καὶ οὐ κατὰ Χριστόν·
2:16-19 Μὴ οὖν τις ὑμᾶς κρινέτω ἐν βρώσει καὶ ἐν πόσει ἢ ἐν μέρει ἑορτῆς ἢ νεομηνίας ἢ σαββάτων· 17 ἅ ἐστιν σκιὰ τῶν μελλόντων, τὸ δὲ σῶμα τοῦ Χριστοῦ. 18 μηδεὶς ὑμᾶς καταβραβευέτω θέλων ἐν ταπεινοφροσύνῃ καὶ θρησκείᾳ τῶν ἀγγέλων, ἃ ἑόρακεν ἐμβατεύων, εἰκῇ φυσιούμενος ὑπὸ τοῦ νοὸς τῆς σαρκὸς αὐτοῦ, 19 καὶ οὐ κρατῶν τὴν κεφαλήν, ἐξ οὗ πᾶν τὸ σῶμα διὰ τῶν ἁφῶν καὶ συνδέσμων ἐπιχορηγούμενον καὶ συμβιβαζόμενον αὔξει τὴν αὔξησιν τοῦ θεοῦ.
What I've noticed for years is that, while Galatians regularly uses the plural to describe the false teachers, Colossians always and only describes him in the singular. (The use of the singular in Galatians 5:10b, amid the other plurals, underscores that not one of the false teachers will be excepted from God's judgment.)
So why is it always assumed that there were false teachers, plural? Paul only describes one. And all it takes is one charismatic, winsome, persuasive, dynamic individual. It only takes a little leaven, after all.
The moral: read closely, don't assume. Just because "everyone" has always said something, don't assume it's true.
Just one such dangerous false teacher warranted this focused and wondrous cautionary blast from the apostle's pen.
Very instructive to us today.