While “The Vision of Sir Launfal” contains various thematic concerns such as heroism, charity, and humanitarianism, the excerpt that begins, “And what is so rare as a day in June?” (Line 33) stands as an exemplary summation of one prevalent theme. This excerpt is often chosen for reading and recital alone and is the most well-known and well-loved part of the poem. In the style of the Romantic movement, Lowell idealizes nature and its power to offer humans a refuge from the toil and routine of everyday life in just a single line. The evocation of the perfect early summer day, therefore, with its riotous explosion of lifeforce, color, sights, and sounds underscores the rest of the poem.

From the outset, Lowell portrays the day as a harmonious scene, which Heaven, or God, desires to be “in tune” like instruments in an orchestra playing together. The many references to hearing and the production of the sounds of the countryside reinforce this notion of a symphony: “murmur,” “listen,” “sings,” “whispering,” “lowing,” “crowing,” and the perfection of the day can be appreciated through listening alone: “We may shut our eyes, but we cannot help knowing / That skies are clear and grass is growing” (Lines 67-68).