Philosophy gets its marching orders in this sonnet, and the places it is sent to explain why. The speaker tells it to go to ancient woods below a mountain crest, to a lonely bower, to a murmuring brook, to caverns where the wind moans. All of these are hushed, sad and secluded, and Philosophy is told to stay in them. Only in the last line does the quarrel come clear. Philosophy has been boasting that it can heal a lover's wound, and the speaker won't hear it. The central idea is that reason, however calm and well supplied with remedies, is no use against heartbreak. The best it can do is keep company with the gloomy scenery that feeling already owns.
The form builds this rejection carefully. The octave is Petrarchan, rhyming ABBAABBA on just two sounds (crest, lour, bow'r, rest; nest, hour, flow'r, breast). That tight, returning pattern suits a landscape of echoes. The sestet then loosens into CDCDCD, and the last rhyme matters. "Wound" lands beside "round" and "bound," so the lover's injury is tied in sound to the imprisoned breezes a few lines earlier. "Philosophy," meanwhile, rhymes with "by" and "sky," drifting off among the airy words. The meter is steady iambic pentameter, kept in shape by squeezed forms like "bow'r," "med'cines" and "slumb'ring." The line "Be these thy pleasures, dull Philosophy!" fits exactly ten syllables around a long, clumsy word, which gives the insult a faintly comic weight.
Repetition does much of the work. "Go" opens line after line ("go seek," "Go, where," "Go, cull," "Go, where"), and each repetition sounds more like a dismissal than a suggestion. The whole poem is one sentence-long command, and the speaker's real subject, a wounded lover, is withheld until the final line.
The time imagery is especially careful. Noon appears three times, each time changed: first as "mid-day glooms," a contradiction in which the brightest hour turns dark; then as "life's fervid noon," which Philosophy is accused of wasting "in fancied rest"; and finally as the noon that "fades slowly down the sky." "Fancied" is a sharp word here. The speaker says Philosophy's calm is only imagined, a pretend peace. The temperature words add to this. Philosophy has a "cold and reas'ning breast," while life's noon is "fervid," so the speaker's world burns with feeling and Philosophy's does not.
The poem also develops a medical conceit. Philosophy is pictured as a kind of herbalist, told to "cull the dew-drops from each potent flow'r / That med'cines to the cold and reas'ning breast." The last line returns to the image with "balm," the soothing ointment Philosophy "vaunts." The cure is offered like a quack's remedy, and by the end the speaker has refused it.
The sound of the sestet shows what the speaker sets against that remedy. "Sadness sweet" is an oxymoron, a grief that has its own pleasure. The brook's "liquid lapse steals by," with its slippery l-sounds, and the zephyrs, gentle winds that are usually playful, are shown "slumb'ring" and moaning, "in caverns bound." Judging by the imagery, the speaker sees in these trapped, murmuring winds a picture of grief that has nowhere to go. Philosophy has no answer to that.
What makes the sonnet interesting is how it argues. It gives no reasoned case against reason. It persuades by atmosphere and by a mildly mocking tone, packing Philosophy off to the kind of place where a heartbroken person might go to grieve. The poem implies that Philosophy would be an intruder there, a cold visitor among things that simply feel. The title marks it as Sonnet XXVI, so it presumably belongs to a longer sequence, but it stands well alone as a compact, slightly sarcastic defence of feeling over argument.