Of this entangled sentence I can draw no sense from the present
reading, and therefore imagine that the author gave it thus:

_For_ he, _a spirit of persuasion, only
Professes to persuade_.

Of which the meaning may be either, that _he alone, who is a
spirit of persuasion, professes to persuade the king_; or that,
_He only professes to persuade_, that is, _without being so
persuaded himself, he makes a show of persuading the king_.

II.i.242 (44,3) [Ambition cannot pierce a wink beyond] That this is
the utmost extent of the prospect of ambition, the point where
the eye can pass no further, and where objects lose their
distinctness, so that what is there discovered, is faint, obscure,
and doubtful. (rev. 1778, I,50,4)

II.i.251 (44,5)

[though some cast again;
And, by that destiny, to perform an act,
Whereof what's past is prologue; what to come,
In yours, and my discharge.]

These lines stand in the old edition thus:

--_though some cast again;
And, by that destiny, to perform an act,
Whereof what's past, is prologue; what to come,