e. Such a labour would provide matter for a whole book.[201]
Here we shall content ourselves with indicating the general rules
governing this kind of reasoning, and the precautions to be taken
against the most common errors.

The argument rests on two propositions: one is general, and is derived
from experience of human affairs; the other is particular, and is
derived from the documents. In practice, we begin with the particular
proposition, the historical fact: Salamis bears a Phoenician name. We
then look for a general proposition: the language of the name of a city
is the language of the people which founded it. And we conclude:
Salamis, bearing a Phoenician name, was founded by the Phoenicians.

In order that the conclusion may be certain, two conditions are
necessary.

(1) The general proposition must be accurately true; the two facts which
it declares to be connected must be connected in such a way that the one
is never found without the other. If this condition were completely
satisfied we should have a _law_, in the scientific sense of the word;
but in dealing with the facts of humanity--apart from those physical
conditions whose laws are established by the regular sciences--we can
only work with empirical laws obtained by rough determinations of
general facts which are not analysed in such a manner as to educe their
true causes. These empirical laws are approximately true only when they
relate to a numerous body of facts, for we can never quite know how far
each is necessary to produce the result. The proposition relating to the
language of the name of a city does not go enough into detail to be
always true. Petersburg is a German name, Syracuse in America bears a
Greek name. Other conditions must be fulfilled before we can be sure
that the name is connected with the nationality of the founders. We
should, therefore, only employ such propositions as go into detail.

(2) In order to employ a general proposition which goes into detail, we
must have a detailed knowledge of the particular fact; for it is not
till after this fact has been established that we look for an empirical
general law on which to found an argument. We shall begin, then, by
studying the particular conditions of the case (the situation of
Salamis, the habits of the Greeks and Phoenicians); we shall not work
on a single detail, but on an assemblage of details.

Thus, in historical reasoning it is necessary to have (1) an accurate
general pr