'Upon' or 'over' signifies being spiritually higher, or interior.

(References: Apocalypse Revealed 900)

900. And over the gates twelve angels, with names written on them, which are those of the twelve tribes of the children of Israel. This symbolizes the Divine truths and goods of heaven in those concepts, which are also the Divine truths and goods of the church, and at the same time safeguards to keep someone from entering into them unless he does so from the Lord.

The twelve angels symbolize here all the truths and goods of heaven, since in the highest sense angels symbolize the Lord, in a more general sense heaven, which is composed of angels, and in a more particular sense the truths and goods of heaven from the Lord. See nos. 5, 170, 258, 344, 415, 465, 647, 648, 657, 718. Here they symbolize the truths and goods of heaven, because the statement follows, "with names written on them, which are those of the twelve tribes of the children of Israel," and these symbolize all the truths and goods of the church (no. 349).

Being over the gates means, symbolically, in those concepts, inasmuch as "over" in the Word symbolically means "within." The reason is that the highest component in sequential order becomes the inmost in concurrent order. Consequently the third heaven is called both the highest heaven and the inmost heaven. That is why "over the gates" symbolically means in the concepts of truth. The names written on the angels symbolize their whole character, thus also the character within them, for every quality in outward expressions originates from inner attributes.

It is apparent that the same words symbolize safeguards to keep someone from entering the church without having those concepts from the Lord, because the angels were seen standing over the gates, and the names of the tribes of Israel were also written on them.

We say that the truths and goods of heaven and the church are present in the concepts coming from the Word that serve to introduce into the church, because when concepts of truth and good from the Word have in them a spiritual quality from heaven from the Lord, they are called not concepts, but truths. But if those concepts do not have in them a spiritual quality from heaven from the Lord, they are nothing more than articles of knowledge.