The Pi are Metaphorical pieces, in which the poet has under his language
a different meaning from what it expresses,--a meaning which there
should be nothing in that language to indicate. Such a piece may be
compared to the AEsopic fable; but, while it is the object of the fable
to inculcate the virtues of morality and prudence, an historical
interpretation has to be sought for the metaphorical pieces of the Shih.
Generally, moreover, the moral of the fable is subjoined to it, which is
never done. in the case of these pieces.

The Hsing have been called Allusive pieces. They are very remarkable,
and more numerous than the metaphorical. They often commence with a
couple of lines which are repeated without change, or with slight
rhythmical changes, in all the stanzas. In other pieces different
stanzas have allusive lines peculiar to themselves. Those lines are
descriptive, for the most part, of some object or circumstance in the
animal or vegetable world, and after them the poet proceeds to his
proper subject. Generally, the allusive lines convey a meaning
harmonizing with those which follow, where an English poet would begin
the verses with Like or As. They are really metaphorical, but the
difference between an allusive and a metaphorical piece is this,--that
in the former the writer proceeds to state the theme which his mind is
occupied with, while no such intimation is given in the latter.
Occasionally, it is difficult,. not to say impossible, to discover the
metaphorical idea in the allusive lines, and then we can only deal with
them as a sort of refrain.

In leaving this subject, it is only necessary to say further that the
allusive, the metaphorical, and the narrative elements sometimes all
occur in the same piece.