A man asks the speaker what all the shouting is about, and the speaker finds he can't answer. There is plenty to shout about, he insists, but he doesn't know how to put it into words the man would understand. The trouble isn't a lack of causes. It's the gap between the noise of public life and any plain explanation of it.
When the man keeps pressing, the speaker finally gives in and tells him "all." What follows is an odd jumble: colts who broke a sacred oath, a border guard, and then Alexander, "big man, halfway into india." The list slides from the small to the grand, and the explanation collapses into something half-mythic and half-absurd. The poem seems to suggest that big public quarrels, once you try to explain them, sound strange and disconnected.
The mood is dry and wry. The speaker sounds tired, a little amused, and quietly skeptical about how much any of this noise means.