Seyton!--I am sick at heart,-- by the way Macbeth begins by calling upon Seyton, twice, the way it interrupts itself and then begins again, and then interrupts itself once more to call for Seyton again. I vacillated between writing "the way it interrupts itself" and "the way he interrupts himself." But it's the speech that's interrupting itself: the sense of social agency that belongs to a person speaking is over now, or all but over.
When I behold--Seyton, I say!--This push
Will cheer me ever, or disseat me now.
I have lived long enough: my way of life
Is fall'n into the sear, the yellow leaf;
And that which should accompany old age,
As honour, love, obedience, troops of friends,
I must not look to have; but, in their stead,
Curses, not loud but deep, mouth-honour, breath,
Which the poor heart would fain deny, and dare not. Seyton!
This is the first time that Macbeth calls on Seyton, the first time he's mentioned. Shakespeare was writing Antony and Cleopatra at the same time as Macbeth, and in both plays he is interested in the last unimportant figures who stay loyal to the end, whose loyalty is only noticeable, who are themselves only noticeable, at the end (in A&C it's the schoolmaster Antony sends to negotiate with Caesar). Seyton matters here because he's the only person Macbeth can count on, because Macbeth still knows that persons are what you count on, that being a person, being able to speak, means being able to speak with someone, to have them care what you say.
I think I'm obsessed by the minimalism of this soliloquy (as in sonnet 73, the language is headed towards the lesser adjectives: sear to the understated yellow; cf. yellow leaves, or none, or few, as though "few" were fewer still than none, as yellow is consciously less sublime, less an achievement, than sear). "Honour" isn't replaced by abasement but by "mouth-honour," a repetition with a difference that is not revolution. And he must not look to have these things: it's not just that he won't have them, but that he can't dally with their false surmise. But he can call Seyton, good air, his only friend.
"When I behold--": prelude to some grand comment on life and its depths, as in the roughly contemporaneous Sonnet 12:
When I do count the clock that tells the time,Shakespeare questions even the young man's beauty and its defense against time, when he beholds the violet past prime; Marvell worries, "When I behold the poet, blind yet bold," that Milton will ruin the sacred truths; Wordsworth's heart leaps up when he beholds a rainbow in the sky. But Macbeth doesn't need to finish the thought: there's no lesson to be learned here, no reaction that matters, no when which marks any sort of achievement or perspective. He has lived long enough to be past whens (she should have died hereafter, either way, so when doesn't matter).
And see the brave day sunk in hideous night;
When I behold the violet past prime,
And sable curls, all silvered o'er with white;
When lofty trees I see barren of leaves,
Which erst from heat did canopy the herd,
And summer's green all girded up in sheaves,
Borne on the bier with white and bristly beard,
Then of thy beauty do I question make,
That thou among the wastes of time must go,
Since sweets and beauties do themselves forsake
And die as fast as they see others grow;
And nothing 'gainst Time's scythe can make defence
Save breed, to brave him when he takes thee hence.
I love this soliloquy, I think, because it doesn't state anything, any insight, any generalization, or rather it's all generalization, since there are no particulars that matter any more, nothing he may look to have. "The poor heart" isn't it's own, but it's what all hearts are now, thanks to him. He calls Seyton, I think, partly to interrupt these thoughts, but partly to confirm them: calling Seyton and being alone are the same thing. Not that Seyton is indifferent to him, but that being alone is the human condition in a different way from the way we imagined. It's not that we're irremediably separated from each other; it's that we're alone together, that we think for others (that's what soliloquies are always about), but what we think about for them is being alone.