sonnetLI

Thus can my love excuse the slow offence
Of my dull bearer when from thee I speed:
From where thou art why should I haste me thence?
Till I return, of posting is no need.
O! what excuse will my poor beast then find,
When swift extremity can seem but slow?
Then should I spur, though mounted on the wind,
In winged speed no motion shall I know,
Then can no horse with my desire keep pace.
Therefore desire, (of perfect'st love being made)
Shall neigh, no dull flesh, in his fiery race;
But love, for love, thus shall excuse my jade-
   Since from thee going, he went wilful-slow,
   Towards thee I'll run, and give him leave to go.

A sequel to the previous sonnet, continuing the story of the lover's journey, and anticipating his eventual return to his beloved, when, as he foresees it, in his eagerness he will outrun even the fastest horse. On first impressions this sonnet seems to describe the return journey, but in fact it only speculates on what that journey might be, while in reality the speaker is still probably travelling away from the youth.

The poem is a remarkable tour-de-force of motion, with words of swiftness and slowness tumbling over each other. Almost every line contains some reference to the rapidity of desire or the dulling drag of reality.

Thus one finds slow; dull; speed; haste; posting; excuse; swift extremity; slow; spur; mounted on the wind; winged speed, no motion; keep pace; desire; dull flesh; fiery race; excuse; going, wilfull slow; run; give leave, go.  These are not all words of motion, but in the context they take up the colours of their surroundings and, like the steed of desire, which is made of the most perfect love, gallop away on the wind.

There are considerable difficulties in attaching precise meanings to the thoughts expressed in lines 9-14, and that is perhaps precisely what we are intended not to do. The range of meanings is dense and elusive, suggesting both the speed of thought, desire, love and devotion, in terms of winged flight (Pegasus), fiery steeds, the winds, the sightless couriers of the air, the horsemen of the apocalypse, as well as the occasional reminder of the dull flesh, poor beasts and the muddy vesture of decay. But it is desire (of perfectest love being made) which in the end triumphs, as the poet rushes forward to the beloved on the swift wings of thought, and material means of transport are turned loose and given leave to wander and to pasture as they please.

The 1609 Quarto Version

THus can my loue excuſe the ſlow offence,
Of my dull bearer,when from thee I ſpeed,
From where thou art,why ſhoulld I haſt me thence,
Till I returne of poſting is noe need.
O what excuſe will my poore beaſt then find,
When ſwift extremity can ſeeme but ſlow,
Then ſhould I ſpurre though mounted on the wind,
In winged ſpeed no motion ſhall I know,
Then can no horſe with my deſire keepe pace,
Therefore deſire(of perfects loue being made)
Shall naigh noe dull fleſh in his fiery race,
But loue,for loue,thus ſhall excuſe my iade,
   Since from thee going he went wilfull ſlow,
   Towards thee ile run,and giue him leaue to goe.

Commentary

1. Thus can my love excuse the slow offence
Thus - referring to the explanation of the horse's lack of speed given in the previous sonnet. Also looking ahead to lines 3-4. my love = my love for you, (which will find reasons to excuse the horse's slowness). But a secondary meaning is the youth himself, who could be imagined as joining in the analysis of love's swiftness and time's slowness. 3-4. slow offence = offensive slowness; the sin of moving in a dull and sluggardish way. Compare swift extremity of line 6.
2. Of my dull bearer when from thee I speed:
my dull bearer - the tardy horse. Also reminiscent of 'one who bears, one who suffers'.
3. From where thou art why should I haste me thence?
Why should I speed away from you?
I haste me - modern usage would be 'I hasten', without the reflexive me. Cf: Weary with toil, I haste me to my bed, 27.
thence
= from there.
4. Till I return, of posting is no need.
of posting = of using post horses, and hence travelling by the fastest possible means. Over 100 miles per day could be achieved by the determined use of post horses, which were stationed at inns on main highways, chiefly for the use of those on government business. The system enabled frequent changes of horse to be made. Hence phrases such as haste-post-haste came into the language.

OED - post. v.1. cites: 1598 Hakluyt Voy. I. 65 Riding as fast as our horses could trot (for we had fresh horses almost thrise or four times a day) we posted from morning till night.

5. O! what excuse will my poor beast then find,
O! What excuse - sc. what excuse for not running fast enough to satisfy the wish of the rider.
6. When swift extremity can seem but slow?
swift extremity = swiftness which is at the extreme of all possible speed; extreme swiftness.
7. Then should I spur, though mounted on the wind,
Then = when the time comes for me to return.
should I spur, though etc. = I would indeed use the spur, even though I were etc.
8. In winged speed no motion shall I know,
It will seem as if even winged flight is like standing still.
9. Then can no horse with my desire keep pace.
(And) no horse will be able to run as fast as I desire it to run. My desire to be with my love is so keen that it seems to leap over distance and nothing can keep pace with it. Lines 9 and 10 seem to be tacked on as additions to line 7, not so much qualifying it as as adding further thoughts which illustrate the poet's eagerness to be going and his anticipation of what he will do then when the journey begins.

The punctuation of 8-14 is problematic. Q does not help much, as it provides only commas for 5-14, implying that the whole is one long sentence. But Therefore of line 10 seems to start a sentence, and I have punctuated accordingly. I have retained the brackets also, which most editors discard. The mere fact that the poem deals with headlong motion makes punctuation of less importance, and we could perhaps abandon it entirely. But this would probably be too disturbing for a modern reader, accustomed to use punctuation as an aid to understanding. In addition, fidelity to the original edition does have some virtue, so one should retain it wherever possible if it does not violate common sense, or if the proposed change does not significantly improve our understanding, or if it is not too much at variance with modern practice.

10. Therefore desire, (of perfect'st love being made)
Qs perfects is usually emended either to perfect or perfect'st as here. The phrase in brackets seems to qualify desire as though fearing that it might be interpreted as lust, or else desiring to show that desire is of a pure and ethereal nature, made of air and fire, as in 44 and 45, and capable of phenomenal speed.
11. Shall neigh, no dull flesh, in his fiery race;
My disembodied desire shall neigh, like a spirited stallion in a turbulent race, expressing its energy and eagerness to reach the goal. It will not be like an ordinary piece of dull horse flesh.

The line is generally reckoned to be difficult, with no single meaning having predominance. But it is clear that some comparison is being made between desire and a spirited horse, the comparison being in the end detrimental to the horse. Since race has several distinct meanings (contest of speed, genus, fast current), it is obvious that several meanings could be hammered from the line, especially as his could apply to desire or to horse indifferently. Desire both is and is not a fiery steed, and in the end it discards all bestial existence in its swift flight through the ether of thought.

12. But love, for love, thus shall excuse my jade-
love, for love = my love for you, or love personified, shall, for the sake of that love, or our love, or for the sake of you, or both, or all, shall etc.
jade a tired horse; a worn out, useless horse.
13. Since from thee going, he went wilful-slow,
from thee going = when leaving you; he - my jade;
wilful-slow = deliberately slowly, obstinately slowly.
14. Towards thee I'll run, and give him leave to go.
give him leave to go = dismiss him, send him packing, let him do as he pleases. The basic meaning of 'to grant permission' in this context acquires a slighltly contemptuous tone, especially as it is applied to a horse, not to a human. Since the horse is so useless he may be turned away. Shakespeare uses the phrase 'to give leave to' more than 80 times in the plays, often at very poignant moments. It was much more common then than now. Some examples are recorded below.

FALSTAFF My lord, I beseech you, give me leave to go
Through Gloucestershire
2H4.IV.3.80-1.

Your grace shall give me leave, my Lord of York,
To be the post, in hope of his reward.
2H6.I.4.77-8.

I beseech your majesty, give me leave to go;
Sorrow would solace and mine age would ease
. 2H6.II.3.20-1.

And, when thou hast done this chare, I'll give thee leave
To play till doomsday. Bring our crown and all
. AC.V.2.230-1.

and if I bring thee not something to eat, I will give thee leave to die: but if thou diest before I come, thou art a mocker of my labour. Well said! AYL.II.6.12-14.