愛という光 means "The light which is called Love", but why is と used? Why does 見る mean "to see" but と見る means something like "it was judged to be"?
What function is と serving?
と is frequently used as a "quoting" particle, for thoughts or for speech.
〜と思います is "I think that〜", with the thought being "quoted" coming in the 〜. Similarly, you can have 〜と考えます (I think that 〜), 〜と信じます (I believe that 〜), and similar examples.
Likewise, と言う used with the kanji means "I (will) say that〜".
However, という used without the kanji tends to indicate that the と言う from which it is derived is acting grammatically, and is thus often better translated as "that is" in these circumstances. But "that is called" is usually fine at getting the essence of the meaning across, if a bit unnatural. There are a tonne of more complex grammatical constructions which use という (e.g. ということ, というと, というもの, というわけ etc.), so be careful as to what proceeds and follows という in general.
Extending the above examples in the same way, 〜と見る is more along the lines of "see that〜" or "regard as〜" -- it's a somewhat more abstract sense of "seeing", e.g. understanding a thought, hence you mark it with the quoting particle と.
This と simply marks quoted speech like the speech marks "" in English. The difference is that in English we only ever use "" for direct quotes e.g.
He said "I'm going to Japan".
but we don't use "" for indirect quotes e.g.
He said he was going to Japan.
However, in Japanese と would be required for both of these.
と思う works pretty much the same way. With と見る, と also marks what someone thought, but it might seem a little more abstract because we don't tend to use it with direct quotes in English.
He judged that the coffee was disgusting.
"This coffee is disgusting" he judged. -- this one seems a bit weird to me.
Finally, the と in 愛という光 is grammatically the same as above. You could break it down as "The light which people say is love", and と would mark the indirect quote "this is love". But, this is a really unnatural and awkward thing to do. Because という appears so often like this I just tend to think of it as a single unit with the meaning "which is called". XというY = "Y which is X", "Y which is called X" or even just "YX".