This poem is pretty much like all of those thoughtful thoughts that you have when you come up with the perfect way to describe a really intense experience you've just had. You know that great song that you can't get out of your head? Or maybe that beautiful sunset you watched on one of the last days of summer. It catches you. Maybe you can't quite come up with the language to express its sticking power – and that's where poets like Auden come in.
His poem is not full of fluffy language or alliteration or any other of those nice tricks that poets like to pull out of their bags. In fact, it's not full of tricks at all. The only time that our speaker gets fancy with adjectives is when he's describing a baby's birth and a ship – and even then, he only uses two words to convey his excitement. As far as poets go, that's as laid-back as it gets.
Somehow, though, this poem never manages to sound like it's an internal monologue. Our speaker never second-guesses himself or pauses to readjust his thinking. There's something neatly (and maybe even eerily) fluid in his movement from philosophy to description. He's trying to explain what he's just seen – maybe to a close friend, or maybe just to a sympathetic ear. He's not out to score any points by talking big. He's just sharing some thoughts that an awfully beautiful painting inspired.
Then again, there's a sort of deliberate tongue-in-cheekness to all of the adjectives that our speaker is tossing around, especially in the last section. He sounds so…happy. Does that mean that Icarus's flight is a silly one? Perhaps. But does that also mean that his fall is not at all troubling? Well, that's where we begin to suspect that our speaker's choice of adjectives might be just a bit diabolical. On second thought, too many happy adjectives make him sound a bit sly – almost as if he's slightly more conscious of his audience than we might otherwise have thought.