The "for" in v.1 indicates that Paul is giving evidence for the struggle for their maturity he refers to in 1:28-29. He want them to know that even though he hasn't seen them face to face (vv. 1,5) he is devoted to their "full assurance" (v. 2) and to their "firmness of faith in Christ" (v. 5). To this end he continues to paint an irresistible picture of who Christ actually is. In Him are "hidden all the treasures of wisdom and knowledge" (v. 3).
Θέλω γὰρ ὑμᾶς εἰδέναι ἡλίκον ἀγῶνα ἔχω ὑπὲρ ὑμῶν καὶ τῶν ἐν Λαοδικείᾳ καὶ ὅσοι οὐχ ἑόρακαν τὸ πρόσωπόν μου ἐν σαρκί,
(Let me substantiate the struggle for your good I mentioned in 1:29) For I want you to know how great a struggle I have for you and for those at Laodicea and for all who have not seen me face to face,
ἵνα παρακληθῶσιν αἱ καρδίαι αὐτῶν
in order that their hearts may be encouraged,
συμβιβασθέντες ἐν ἀγάπῃ
( because we all [cf. 5b] have been) knit together in (the sphere of) love,
καὶ εἰς πᾶν πλοῦτος τῆς πληροφορίας τῆς συνέσεως,
and (the positive purpose is that you will have) all the riches of full assurance of understanding
εἰς ἐπίγνωσιν τοῦ μυστηρίου τοῦ θεοῦ, Χριστοῦ,
( namely that you will have) the knowledge of God’s mystery , which is Christ,
ἐν ᾧ εἰσιν πάντες οἱ θησαυροὶ τῆς σοφίας καὶ γνώσεως ἀπόκρυφοι.
(the reason I want you to know Christ is because) in Him are hidden all the treasures of wisdom and knowledge.
I say this (for a negative purpose as well)
ἵνα μηδεὶς ὑμᾶς παραλογίζηται ἐν πιθανολογίᾳ.
in order that no one may delude you with plausible arguments.
εἰ γὰρ καὶ τῇ σαρκὶ ἄπειμι,
For though I am absent in body,
ἀλλὰ τῷ πνεύματι σὺν ὑμῖν εἰμι,
yet I am with you in spirit,
( in that I am) rejoicing
καὶ βλέπων ὑμῶν τὴν τάξιν καὶ τὸ στερέωμα τῆς εἰς Χριστὸν πίστεως ὑμῶν.
( because I am) seeing your good order and the firmness of your faith in Christ.