Final answer:
Thoreau's use of imagery in the given Walden excerpt conveys the insignificance of time against the backdrop of eternity, reflecting his broader philosophy that advocates for a life of simplicity and intentionality.
Step-by-step explanation:
In the excerpt from Walden, Thoreau primarily uses imagery to illustrate his belief that the passing of hours and days is irrelevant. He describes time as a stream in which he fishes, a metaphor that serves to show how time is but a shallow stream in the vast presence of eternity. Thoreau's reflection is on the transience of time and the enduring nature of the eternal, thus aligning with his overarching theme within Walden that encourages living simply and with deliberate intention, undistracted by the superficial urgency that governs the lives of many.
Throughout Walden, Thoreau conveys his ideas of simplicity and deliberate living. He advocates for a life stripped of societal complexities, reinforcing the idea that the essence of life goes beyond materialistic pursuits. His time at Walden Pond is characterized by a close connection with nature and the practice of self-reliance which parallels the sentiment expressed in the quote.