John 1:4 - Articles and Subject

[Geoff]

John 1:4 - ἐν αὐτῷ ζωὴ η}ν, καὶ ἡ ζωὴ η}ν τὸ φῶς τῶν ἀνθρώπων.
In the second clause, it seems obvious that "life" is the subject, but grammatically, how is this known since the predicate nominative has the article aswell?

also, in the first clause, is the article missing to show that "life" here is qualitative?

[Skylax]

John 1:4 - ἐν αὐτῷ ζωὴ η}ν, καὶ ἡ ζωὴ η}ν τὸ φῶς τῶν ἀνθρώπων.
In the second clause, it seems obvious that "life" is the subject, but grammatically, how is this known since the predicate nominative has the article aswell?

The complement has the article to denote an identity with the subject, so the life = the light (and reciprocally). Here "life" is to be understood as the subject... because it is the thing it is spoken about.

also, in the first clause, is the article missing to show that "life" here is qualitative?

I don't think so. Without article, it means "Life", denoting a concept. I think it would be also "life" without an article in the English translation. In the following clause, the article indicates that it is again about "the" life mentioned before.