makes the moon to be moved by the motion of the earth, and carried
about her orb as a dependent of hers. Mascardi, in his discourse of
the "Doppia Favola," or double tale in plays, gives an instance of
it in the famous pastoral of Guarini, called Il Pastor Fido, where
Corisca and the Satyr are the under-parts; yet we may observe that
Corisca is brought into the body of the plot and made subservient to
it. It is certain that the divine wit of Horace was not ignorant of
this rule--that a play, though it consists of many parts, must yet
be one in the action, and must drive on the accomplishment of one
design--for he gives this very precept, Sit quod vis simplex
duntaxat, et unum; yet he seems not much to mind it in his satires,
many of them consisting of more arguments than one, and the second
without dependence on the first. Casaubon has observed this before
me in his preference of Persius to Horace, and will have his own
beloved author to be the first who found out and introduced this
method of confining himself to one subject.

I know it may be urged in defence of Horace that this unity is not
necessary, because the very word satura signifies a dish plentifully
stored with all variety of fruits and grains. Yet Juvenal, who
calls his poems a farrago (which is a word of the same signification
with satura), has chosen to follow the same method of Persius and
not of Horace; and Boileau, whose example alone is a sufficient
authority, has wholly confined himself in all his satires to this
unity of design. That variety which is not to be found in any one
satire is at least in many, written on several occasions; and if
variety be of absolute necessity in every one of them, according to
the etymology of the word, yet it may arise naturally from one
subject, as it is diversely treated in the several subordinate
branches of it, all relating to the chief. It may be illustrated