The author spoke about the world and why the world would find communion with God and fellowship with the saints to be undesirable.
Communion with God is desirable
John told his readers that unbelievers would indeed see disadvantages in the fellowship of believers, but those disadvantages were only apparent to the worldly eye. But to believers, to the saints, this fellowship is very honorable, it's glorious and very desirable.
We can boldly say with the apostle, "the Saints of God have communion with Him."
and indeed our fellowship is with the Father and with his Son Jesus Christ. (1 John 1:3)
This fellowship is holy and spiritual and it is written in the Scriptures so succinctly that Owen will fully upack it and open the meaning up to us.
The block of the day
To prevent or remove these and the like exceptions, the apostle gives them to whom he wrote to know (and that with some earnestness of expression), that notwithstanding all the disadvantages their fellowship lay under, unto a carnal view, yet in truth it was, and would be found to be (in reference to some with whom they held it), very honourable, glorious, and desirable.
For “truly,” saith he, “our fellowship is with the Father, and with his Son Jesus Christ.”This being so earnestly and directly asserted by the apostle, we may boldly follow him with our affirmation, — namely, “That the saints of God have communion with him.” And6a holy and spiritual communion it is, as shall be declared. How this is spoken distinctly in reference to the Father and the Son, must afterward be fully opened and carried on