I've read in several places that these are lines from a poem by Archibald MacLeish:

"...ours is the late, last wisdom of the afternoon. We know that love, like light, grows dearer toward the dark."

I've seen the whole quote and separate quotes of oe half or the other, but can’t find any more – like the whole poem’s or its title - can anyone help, please ?

I know MacLeish wasn't just a poet, so suppose it could be from his prose, but the places I've found it cite it as from a poem.

Looks like a job for Ilza.

Les

She probably has it memorized, but I see it his Collected Poems 1917-1982 pp 33-35. Two poems there, The Old Gray Couple (1) and (2). This quote is the last stanza of (2):

[...]

She: And that's your reason? -- that old lovers see
their love because they know now what its loss will be?

He: Because, like Cleopatra in the play,
they know there's nothing left once love's away ...

She: Nothing remarkable beneath the visiting moon ...

He: Ours is the late, last wisdom of the afternoon.
We know that love, like light, grows dearer toward the dark.

Thanks, Hugh - another loose end tied up! Isn't it amazing how knowing the context can completely change your conception of a quote - I'd thought the quote implied late love was of great value because it was more realistic and had lasted - the poem is more about it being valued for its rarity, despite it being a rather worn remnant of the real thing - and 'dearer' seems almost to mean more expensive, rather than more precious, in that context.