The speaker in this poem values truth above all else. For this reason, she prefers to see someone in agony (“I like a look of Agony”), because she knows that they aren’t pretending (“Because I know it’s true –“), since people, according to her, don’t fake convulsions or fits (“Men do not sham Convulsion, / Nor simulate, a Throe – “).
She is not just talking about normal agony, though—she is concerned with that agony which precedes death, because this of all things is “Impossible to feign.” The glazing of the eyes (“The Eyes glaze once”), the drops of sweat on the forehead (“The Beads upon the Forehead”), are the physical remnants of the agony preceding death, which even the best actor cannot fake.
“I like a look of Agony,” is yet another Dickinson poem that finds something to admire in those things that are usually feared or vilified. Throughout Dickinson’s poetry, truth is a very slippery thing, and very hard to get at directly, but it is usually valued above all else. This poem is no exception, turning the agony of death into a positive, because it is one of the few things that an observer can see and trust—it is a rare moment of undoubted truth.
This poem is rather unusual, however, because while it finds an admirable quality in the usually not so admirable agony, it is not in the speaker’s own agony, but in that of others. Other Dickinson poems that enact a similar process show, for example, the speaker extolling her own isolation because it means she is not part of the foolish crowd, or appreciating the grief and hardship she has faced because it has made her stronger. The difference in this poem makes its tone different than the others, for here she is wishing pain on another, just so she can trust them, which is not self-sacrificial, but really quite the opposite.
The detailed specifics she reports, additionally, make it clear that she has watched someone in agony, and by her own admission, has enjoyed it -- which makes the poem even more disturbing. She doesn’t just need tears of agony to trust someone, she wants a “Convulsion,” “a Throe,” glazed over eyes, “Beads upon the Forehead.” These are all symbols of the worst kind of pain, even disregarding the fact that it is a pain that ends in death.
This all serves to show just how much this speaker does value the truth. All these horrifying details of the ending of a life are to her valuable details, even decorations (like the “strung” beads), because they are the proof that what she is watching is real, is true. This truth forms a kind of connection between her and the person who is dying, because she trusts them as she cannot trust others.
This poem can also be read as a reflection on Dickinson’s own poetry. She certainly cannot be accused of focusing on the beautiful, the easy, the mundane, and this poem seems to say that that is because pain is required for real truth. The agonized emotions and events she presents in her poetry are to her the most direct route to the truth, even though they still require the imagery, metaphors, and symbols of poetry that stand between the reader and truth, just as she relies on the symbols of pain to know that the subject is in agony.