In “A Passing Glimpse,” Robert Frost emphasizes the need to appreciate nature's beauty despite the busyness and constant change of modern-day life. While riding in a car or on a train, for example, he speeds past flowers without a chance to stop, disembark, and take a long, close look at them. The automobile and railway cars contrast the flora through which they travel. These vehicles represent mechanization, change, and haste. On the other hand, the plants represent nature untouched by man; they develop organically according to their own schedule.
Frost notes that he passes by flowers so quickly that he does not even know their specific names. He can, however, state what flowers they are not:
Not fireweed loving where woods have burnt—
Not bluebells gracing a tunnel mouth—
Not lupine living on sand and drouth.
By beginning each line with “Not,” Frost sets up and stresses the absence of what he sees. In reality, he perceives only a vague blur; in his mind, however, he vividly pictures lovely and graceful firewood, bluebells, and lupine in their natural surroundings.
Through repetition, Frost also emphasizes that imbedded in his “mind” is a list of other flowers. The fact that he offers up other species (that the real flowers are not) illustrates that nature’s beauty is striking enough to be memorable. He notes,
Heaven gives it glimpses only to those
Not in position to look too close.
Although afforded only “glimpses” of flowers as he rushes around, Frost remembers some of them well. By ending the poem with a line that begins “Not,” he recalls the idea of absence; in this case, it is the absence of stillness in modern life. People are not in a position to stop and smell the roses, and they miss the chance to enjoy beauty outside of fleeting moments.