Poetry is the art of recognizing peculiar structures in nature. You don’t understand the structure, you just recognize it. Some people spy out the four leaf clover; you, poet, spy out the four leaf relationship, the four leaf justification.
It is very difficult to do this. Years later a scientist may come to describe and understand the relationship; when this happens, it is appropriate for the scientist to quote the poem at the beginning of her article on the subject.
Example:
In Paradise Regained, Milton writes:
Upon my head, long the decrees of Heav’n
Delay, for longest time to him is short
I : 55-56.
He’s captured the notion of the immeasurability of time. When Kant comes to describe this in Critique of Pure Reason, it would be appropriate for him to quote those lines.