are in algebra, in place of concrete and specified quantities. Moreover,
it should be used as sparingly as the dissecting knife on the body of a
living man. At the risk of forfeiting his life it is an unsafe
experiment.

For a work to become _immortal_ it must possess so many excellences that
it will not be easy to find a man who understands and values them _all_;
so that there will be in all ages men who recognise and appreciate some
of these excellences; by this means the credit of the work will be
retained throughout the long course of centuries and ever-changing
interests, for, as it is appreciated first in this sense, then in that,
the interest is never exhausted.

An author like this, in other words, an author who has a claim to live
on in posterity, can only be a man who seeks in vain his like among his
contemporaries over the wide world, his marked distinction making him a
striking contrast to every one else. Even if he existed through several
generations, like the wandering Jew, he would still occupy the same
position; in short, he would be, as Ariosto has put it, _lo fece natura,
e poi ruppe lo stampo_. If this were not so, one would not be able to
understand why his thoughts should not perish like those of other men.

In almost every age, whether it be in literature or art, we find that if
a thoroughly wrong idea, or a fashion, or a manner is in vogue, it is
admired. Those of ordinary intelligence trouble themselves inordinately
to acquire it and put it in practice. An intelligent man sees through it
and despises it, consequently he remains out of the fashion. Some years
later the public sees through it and takes the sham for what it is
worth; it now laughs at it, and the much-admired colour of all these
works of fashion falls off like the plaster from a badly-built wall: and