1 Thus can my love excuse the slow offence,
Thus can my love forgive the horse's slow pace, my love makes me forgive how slowly we were going, love excuses slowness 'Excuse' = pardon, make acceptable; love itself provides justification for the horse's—and the speaker's—reluctance.
2 Of my dull bearer, when from thee I speed,
Of my slow horse, when I depart from you, my horse moves slowly when we're leaving you, my slow horse when i leave 'Dull bearer' = the horse; 'speed' here means hasten/depart (not move quickly)—the irony is the verb.
3 From where thou art, why should I haste me thence?
From where you are—why should I rush away? why would I want to leave you quickly? why rush from you Rhetorical question: the answer is obvious. Remaining with the beloved requires no haste; departure is inherently unwelcome.
4 Till I return of posting is no need.
Until I return, speed is unnecessary. there's no rush until I'm coming back to you, no hurry until i return 'Posting' = rapid travel (changing horses at post stations); the journey away doesn't warrant such urgency.
5 O what excuse will my poor beast then find,
O what excuse will my poor horse then find, but what excuse will my horse have then, but then my horse can't excuse Shifts to the return journey; now the horse faces the opposite problem—insufficient speed for love's urgency.
6 When swift extremity can seem but slow?
When even the utmost speed seems too slow? when even going as fast as possible isn't fast enough? when all speed seems slow 'Swift extremity' = the ultimate in speed; love's desire transcends even this, making all speed inadequate.
7 Then should I spur though mounted on the wind,
Then would I spur, even if mounted on wind, I'd whip even the wind itself to go faster, i'd spur even the wind 'Wind' = the fastest possible natural element; even this would require spurring—be insufficient.
8 In winged speed no motion shall I know,
At such winged speed, I would feel no journey, going so fast, the trip would feel instantaneous, speed so great the journey vanishes Paradox: at extreme speed, the journey becomes non-existent; motion transcends sensation of movement.
Volta The volta shifts from hypothetical speed ('should I spur though mounted on the wind') to the realization that desire itself, purified by love, becomes the ultimate transport.
9 Then can no horse with my desire keep pace,
Then no horse can match my desire's speed, no horse could ever keep up with how much i want you, no horse can match my longing
10 Therefore desire (of perfect’st love being made)
Therefore desire, made of love's purest form, so desire itself—born of perfect love— desire, perfected by love 'Perfect'st love' suggests love in its most concentrated, undiluted form; desire is love's ultimate expression.
11 Shall neigh no dull flesh in his fiery race,
Shall call upon no dull flesh for its fiery sprint, won't need any animal for its passionate journey, needs no animal vessel 'Neigh' = call upon; 'dull flesh' = the material horse; 'fiery race' = the passionate journey. Desire transcends physical mounts.
12 But love, for love, thus shall excuse my jade:
But love, moving toward love, shall pardon my horse, but love moving toward you will forgive my horse, love excuses the horse 'Love for love' = love moving toward love; the horse ('jade') is pardoned because the speaker now needs no mount but love.
13 Since from thee going, he went wilful-slow,
Since leaving you, he went intentionally slow, because on the way leaving you, he moved slowly on purpose, he was wise to go slow then 'Wilful-slow' = intentionally slow, perhaps even wise; the horse's reluctance on the outward journey was justified.
14 Towards thee I’ll run, and give him leave to go.
Toward you I'll run, and release him from service. toward you I'll run on my own, and let the horse rest. i'll run to you without him The couplet's transformation: on the return journey, the speaker becomes his own vehicle, moved by desire and love alone.