1. The Passage of Time and Memory: The poem describes the gradual loss of memory and the fading of the past. The speaker's "grandmother's voice" is described as "thin, like a spider web," suggesting the fragility of memory. This theme is further reinforced by the repeated use of the word "knock," which can be interpreted as a reminder of the past that keeps intruding on the present.
2. Loss and Grief: The poem also deals with the grief of loss, both personal and universal. The "old man" who knocks on the door might represent a loved one who has passed away. The speaker's inability to remember the old man's name further underscores the theme of loss and the difficulty of holding onto memories.
3. The Uncertainties of Life: The poem explores the sense of confusion and disorientation that can accompany aging and the passage of time. The speaker's inability to recall the old man's name, or even to clearly remember his own past, reflects the uncertainty and fragility of human experience.
4. The Power of Language: The poem can also be seen as an exploration of the power of language and its ability to both preserve and distort memory. The speaker's struggle to find the right words to describe the old man's appearance and the experience of his knock highlights the limitations of language in capturing the complexities of human experience.
Ultimately, the theme of "Knock" is open to interpretation and depends on the reader's individual perspective and experiences. It is a poem that can evoke a range of emotions and resonate with different readers in various ways.