The poem begins with a small claim: nothing is ever completely still. Sound is a kind of movement, and after sound comes the wind. Even the sunshine has clouds behind it, so what looks calm is always shifting underneath.
The speaker seems to be doing very little. Sitting in a corner and counting pebbles is a quiet, almost idle act, yet it sharpens attention. By the end, the focus narrows to the shade under a tree, where leaves dance so slightly that the word "imperceptibly" sits alone on the last line, as if the poem itself is holding its breath.
The mood is calm, patient and observant. The speaker doesn't seem anxious or sad, just attentive, and content to notice. The short lines and wide spaces give the feeling of a slow, careful look at the world. The poem suggests that stillness is something we sense, not something that truly exists, and that paying attention can reveal how much is quietly happening.