so they begin to deny truths that have long been admitted--the vital
power, for example, the sympathetic nervous system, _generatio
equivoca_, Bichat's distinction between the working of the passions
and the working of intelligence; or else they want us to return to
crass atomism, and the like. Hence it frequently happens that _the
course of science is retrogressive._

To this class of writers belong those translators who not only
translate their author but also correct and revise him; a proceeding
which always seems to me impertinent. To such writers I say: Write
books yourself which are worth translating, and leave other people's
works as they are!

The reader should study, if he can, the real authors, the men who
have founded and discovered things; or, at any rate, those who are
recognized as the great masters in every branch of knowledge. Let him
buy second-hand books rather than read their contents in new ones. To
be sure, it is easy to add to any new discovery--_inventis aliquid
addere facile est_; and, therefore, the student, after well mastering
the rudiments of his subject, will have to make himself acquainted
with the more recent additions to the knowledge of it. And, in
general, the following rule may be laid down here as elsewhere: if a
thing is new, it is seldom good; because if it is good, it is only for
a short time new.

What the address is to a letter, the title should be to a book; in
other words, its main object should be to bring the book to those
amongst the public who will take an interest in its contents. It
should, therefore, be expressive; and since by its very nature it must
be short, it should be concise, laconic, pregnant, and if possible