Summary
The speaker compares the passage of summer to the process of grieving, in terms of its quiet transition. She continues in the same vein, describing the way summer slips away subtly. She makes another comparison, this time between this quietness and the middle of a twilight. Finally, she describes nature spending an isolated afternoon with itself.
Analysis
"As imperceptibly as Grief" is Dickinson's complex and allusive rumination on time, loss, and the cycles of nature. She uses the idea of the progression of days and seasons to explore what is lost in the harder-to-quantify passage of moments. She also looks at the way in which these instances of transition occur without being noticed, only for the viewer to feel the immediate absence of whatever moment has just vanished.
The poem opens on a mixed note. The speaker draws a parallel between grief and summer's end ("As imperceptibly as Grief / The Summer lapsed away —"), immediately introducing the themes of time and loss. The word "imperceptibly" serves an important function in the first line. It demonstrates the way in which the movements between the seasons are significant shifts that occur with very little notice. People don't notice the change until it is already complete. We don't notice the transition; only the resulting loss is registered. The next two lines ("Too imperceptible at last / To seem like Perfidy —") tread similar territory. Dickinson uses the word imperceptible once again, marking its contrast with "perfidy" or deception. She is stating that this imperceptibly is not a trick or illusion. It is long-term and enduring. Summer's end arrives with a finality. She is attempting to show the way in which this quality is inherent to these moments of transition. Summer has not fooled the viewer into missing its exit. It is simply too understated to detect.
In the next four lines, the speaker considers two moments of natural silence. The first of these is at night: "A Quietness distilled / As Twilight long begun." The quiet is "distilled" because it is so pointedly present. It is a moment of uninterrupted calm. This becomes particularly apparent in the speaker's mention of a "twilight long begun." She is referring to the middle of a late evening. This choice is also notable in relation to the scene that follows it. It is describing a liminal, transitional time of day, the late twilight that precedes the dawn. In the next two lines, the speaker depicts midday serenity ("Or Nature spending with herself / Sequestered Afternoon —") as nature taking a moment for "herself." The speaker personifies nature here and imagines an afternoon in which "she" is alone. Taken together, these scenes build upon the concepts of the opening. Dickinson is choosing times of day in which nature is still, and time passes without notice. In these moments of "distilled" quiet and "sequestered" calm, there are no viewers. Transitions in the day, the moments between light and darkness, are not being taken note of by anyone. She portrays them as being cloistered, occurring without being viewed. She is reinforcing the idea that these scenes elapse silently.
The dashes that end the second, fourth and eighth lines serve to neatly divide the poem. Each thought is broken up into discreet bits. The dashes demarcate where individual considerations begin and end. This is particularly helpful given the poem's lack of stanzas. The slant rhyme between the even-numbered lines works in a similar fashion. It breaks up the text of the poem into four-line units, aligning neatly (but slyly) with the themes explored in these various sections. The capitalization of specific times ("Summer," "Twilight," and "Afternoon") has a similar effect, allowing them to be viewed as more than just setting, elevating them as concepts. This stylistic choice also aligns well with Dickinson's later exploration of summer as a cherished guest.
