f all statements obtained
by interrogating witnesses. Even apart from the cases where the person
interrogated seeks to please the proposer of the question by giving an
answer which he thinks will be agreeable to him, every question suggests
its own answer, or at least its form, and this form is dictated
beforehand by some one unacquainted with the facts. It is therefore
necessary to apply a special criticism to every statement obtained by
interrogation; we must ask what was the question put, and what were the
preconceptions to which it may have given rise in the mind of the person
interrogated.

(2) The author was badly situated for observing. The practice of the
sciences teaches us what are the conditions for correct observation. The
observer ought to be placed where he can see correctly, and should have
no practical interest, no desire to obtain a particular result, no
preconceived idea about the result. He ought to record the observation
immediately, in a precise system of notation; he ought to give a precise
indication of his method. These conditions, which are insisted on in the
sciences of observation, are never completely fulfilled by the authors
of documents.

It would be useless, therefore, to ask whether there have been chances
of inaccuracy; _there always have been_, and it is just this that
distinguishes a _document_ from an _observation_. It only remains to
look for the obvious causes of error in the conditions of observation:
to inquire whether the observer was in a place where he could not see or
hear well, as would be the case, for example, with a subordinate who
should presume to narrate the secret deliberations of a council of
dignitaries; whether his attention was greatly distracted by the
necessity for action, as it would be on the field of battle, for
example; whether he was inattentive because the facts had little
interest for him; whether he lacked the special experience or general
intelligence necessary for understanding the facts; whether he analysed
his impressions badly, or confused different events. Above all, we must
ask when he _wrote down_ what he saw or heard. This is the most
important point: the only exact observation is the one which is
recorded immediately it is made; such is the constant procedure in the
established sciences; an impression committed to writing later on is
only a recollection, liable to be confused in the memory with other
recollections. _Memoirs_ written several ye