The Four Subjects of Poetry

On Saturday's NPR Weekend Edition, Scott Simon interviewed Edward Hirsch. During the course of the interview, Hirsch cited poet William Matthews's conclusions about the four subjects of poetry, which are

1. I went out into the woods today, and it made me feel, you know, sort of religious.
2. We're not getting any younger.
3. It sure is cold and lonely (a) without you, honey, or (b) with you, honey.
4. Sadness seems but the other side of the coin of happiness, and vice versa, and in any case the coin is too soon spent, and on what we know not what.