sions go
to form a given collective impression, in order that precision may be
attained by a successive consideration of them. This is an indispensable
operation but we must not exaggerate its scope. It is not an objective
method which yields a knowledge of real objects; it is only a subjective
method which aims at detecting those abstract elements which compose our
impressions.[182] From the very nature of its materials history is
necessarily a subjective science. It would be illegitimate to extend to
this intellectual analysis of subjective impressions the rules which
govern the real analysis of real objects.

History, then, must guard against the temptation to imitate the method
of the biological sciences. Historical facts are so different from the
facts of the other sciences that their study requires a different
method.

III. Documents, the sole source of historical knowledge, give
information on three categories of facts:

(1) _Living beings and material objects._ Documents make us acquainted
with the existence of human beings, physical conditions, products of art
and industry. In all these cases physical facts have been brought
before the author by physical perception. But we have before us nothing
but intellectual phenomena, facts seen "through the author's
imagination," or, to speak accurately, mental images representative of
the author's impressions--images which we form on the _analogy_ of the
images which were in his mind. The Temple at Jerusalem was a material
object which men saw, but we cannot see it now; all we can now do is to
form a mental image of it, analogous to that which existed in the minds
of those who saw and described it.

(2) _Actions of men._ Documents relate the actions (and words) of men of
former times. Here, too, are physical facts which were known to the
authors by sight and hearing, but which are now for us no more than the
author's recollections, subjective images which are reproduced in our
minds. When Caesar was stabbed the dagger-thrusts were seen, the words of
the murderers were heard; we have nothing but mental images. Actions and
words all have this characteristic, that each was the action or the word
of an individual; the imagination can only represent to itself
_individual_ acts, copied from those which are brought before us by
direct physical observation. As these are the actions of men living in a
society, most of them are performed simultaneously by several
individual