Time drops in decay,
Like a candle burnt out,
And the mountains and woods
Have their day, have their day;
What one in the rout
Of the fire-born moods
Has fallen away?
Moods by nature are ephemeral. They tend to last only a short time and are generally caused by some event or thought. But Yeats compares moods to things more lasting, specifically mountains and woods, which are also temporary but endure for a long time. So what are the moods that Yeats is writing about?
Since the word “moods” is plural, it is clear he is experiencing more than one mood at the same time. Also, we are told that these moods are born from fire. An obvious mood would be love or passion, a mood clearly associated with fire. But I would also venture to say that one of the moods is associated with creative inspiration, the spark of the creative flame which, if not nurtured, quickly burns out like the candle. And I suspect there is a third mood, relating to divine inspiration or illumination. Again, this “mood” is fleeting, and usually once you realize that you are having a moment of divine connection, it immediately dissipates.
My final thought on this poem may be a bit of a stretch, but as I read it a few times, I could not help but wonder if there is also an allusion to “modes.” When read aloud with an accent, it is possible. If this is the case, then Yeats may also have been asserting that there are various modes of artistic and spiritual expression, and that each mode is also ephemeral and dependent upon the artist and the audience. At some points poetry and literature may be the dominant mode, other times painting, other times music, or film. As such, moods and modes are always changing.
Anyway, these are just my thoughts. Yeats is always challenging, and it seems the more pared down his poems are, the more you have to work to understand them. Feel free to share your thoughts on this one. Cheers!