When 'islands' are contrasted to 'earth' or 'mountains,' they signify the truths of faith, because they are in the sea. They signify doctrinal things which are rituals. 'Islands' signify peoples who are more remote from the worship of God. People who are steeped in the internal sense of the Word, such as angels, do not know what islands are, because they no longer have any concept of such places. Instead they have a perception of more remote worship, like the gentiles outside the church.

'Islands,' in Ezekiel 27:6, signify people in the church in a natural, materially-oriented state but still rational.

(Reference: Apocalypse Explained 406; Isaiah 1, Isaiah 49, 49:1)

35. For the Word of God and the testimony of Jesus Christ. This symbolically means, so as to receive Divine truth from the Word with the heart and so in a state of light, and to acknowledge the Lord's humanity to be Divine.

This we explained in no. 6 above.