The theme of the poem is perseverance (keep in mind that subjects of poetry might alter depending on the reader's subjective ideas). Whatever it goes through, the brook will continue "forever." The brook will endure regardless of the hurdles it must conquer or the number of twists and turns it must take. Thus, the brook represents freedom to some people and imprisonment to others. However, it also represents life, since nothing permanent or stable can be destroyed. Instead, everything changes and evolves. In addition to this idea of impermanence, the brook also symbolizes joy. No matter how difficult or painful your circumstances may be, there will always be hope for a better future. Even though the poet describes the brook as "silent," it is actually singing with all the beauty it has seen over time. This is why people often describe nature as beautiful: because seeing is believing! Finally, the birds help convey the idea of transience by showing that even though things may seem sad now, they will eventually get better. Even though the flowers are now at their lowest ebb, they will rise again after being washed away by the rain. Even though the brook appears to be quiet now, it will start flowing again once more when the rain stops. All these things will happen again next year, and the year after that, and forever more. Transience is important because happiness depends on not being permanently attached to something material or physical.