'Thanatopsis' was written by William Cullen Bryant—probably in 1813, when the poet was just 19. It is Bryant's most famous poem and has endured in popularity due its nuanced depiction of death and its expert control of meter, syntax, imagery, and other poetic devices. The poem gives voice to the despair people feel in contemplating death, then finds peace by viewing death as a harmonious part of nature.
To put it bluntly, “Thanatopsis” is about death. The word thanatopsis itself derives from the Greek roots thanatos (death) and opsis (sight). In other words, the poem always has death in its sights. One of the speaker’s main goals seems simply to make death—and its inevitability—vivid for the poem’s readers. The poem hammers home the fact that death comes for everyone, and voices the despair that such knowledge can cause.
The speaker begins by describing an idyllic scene, in which the natural world itself seems to reflect a person's joyful state of mind. Suddenly, though, frightening thoughts of death intrude on this peace 'like a blight'—or disease—over 'thy spirit.' These 'thoughts / Of the last bitter hour,' of the moments immediately before death, will cause anyone to “shudder, and grow sick at heart.' In other words, thoughts of death can come on suddenly and are extremely disturbing. What's more, these thoughts are unavoidable; the speaker doesn't say 'if' such thoughts come, but rather 'when.'
As if this weren't dark enough, in the second stanza the speaker strikes an even bleaker note, saying that the reader is going to die soon: “Yet a few days, and thee / The all-beholding sun shall see no more,” the speaker says, meaning the sun won’t shine on the addressee because they’ll be buried in the earth. Continuing with this vivid description, the speaker next invites the reader to imagine their body decomposing: “The oak / Shall send his roots abroad, and pierce thy mould.” In other words, the dead body will turn into dirt, through which different plants’ roots will grow.
Next, to underscore that this fate awaits us all, the speaker reflects on all the people who have already died. The speaker frames this discussion by describing the realm of the dead. First, the speaker makes clear just how big this realm is. The dead outnumber the living: “All that tread / The globe are but a handful to the tribes / That slumber in its bosom.” When someone dies, they join an enormous realm that will exist for all eternity.
All people throughout history end up with the dead, from “patriarchs of the infant world” to those who have yet to be born. No one escapes death, not “the kings, / The powerful of the earth—the wise, the good,” nor “matron and maid, / The speechless babe, and the gray-headed man.” The realm of the dead is a crowded place indeed, underscoring the poem's point that death comes for everyone.
The speaker also reminds the reader that none of the joys of living can continue in the realm of the dead. Everyone, eventually, must “leave / Their mirths and their enjoyments.” Human emotions and sensations—the speaker seems to say—don’t exist beyond the grave. The poem thus summons the immensity, strangeness, and scariness of death, impressing the weight of mortality upon the reader. It's a dark take, to be sure, but the speaker isn't necessarily trying to make readers feel bad. Instead, the poem seeks to acknowledge the sharp pang of dread that accompanies thoughts of death, without turning away.
That is, the poem pushes its readers to actually think about the process of dying because such understanding is the first step towards making peace with death.