is to be given to witnesses,--who, and of what dignity, and of what
estimation they are,--whether they seem to deliver their evidence with
simplicity and candor, whether they seem to bring a formed and
premeditated discourse, or whether on the spot they give probable matter
in answer to the questions that are put to them." And there remains a
rescript of the same prince to Valerius Verus, on the bringing out the
credit of witnesses. This appears to go more to the _general_ principles
of evidence. It is in these words:--"What evidence, and in what measure
or degree, shall amount to proof in each case can be defined in no
manner whatsoever that is sufficiently certain. For, though not always,
yet frequently, the truth of the affair may appear without any matter of
public record. In some cases the number of the witnesses, in others
their dignity and authority, is to be weighed; in others, concurring
public fame tends to confirm the credit of the evidence in question.
This alone I am able, and in a few words, to give you as my
determination: that you ought not too readily to bind yourself to try
the cause upon any one description of evidence; but you are to estimate
by your own discretion what you ought to credit, or what appears to you
not to be established by proof sufficient."[45]

The modern writers on the Civil Law have likewise much matter on this
subject, and have introduced a strictness with regard to personal
testimony which our particular jurisprudence has not thought it at all
proper to adopt. In others we have copied them more closely. They divide
Evidence into two parts, in which they do not differ from the ancients:
1st, What is Evidence, or Proof, by itself; 2dly, What is Presumption,
"which is a probable conjecture, from a reference to something which,
coming from marks and tokens ascertained, shall be taken for truth,
until some other shall be adduced." Again, they have labored
particularly to fix rules for presumptions, which they divide into, 1.