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.  Violent and necessary, 2.  Probable, 3. and lastly, Slight and rash.[46] But finding that this head of Presumptive Evidence (which makes so large a part with them and with us in the trial of all causes, and particularly criminal causes) is extremely difficult to ascertain, either with regard to what shall be considered as exclusively creating any of these three degrees of presumption, or what facts, and how proved, and what marks and tokens, may serve to establish them, even those Civilians whose character it is to be subtle to a fault have been obliged to abandon the task, and have fairly confessed that the labors of writers to fix rules for these matters have been vain and fruitless.  One of the most able of them[47] has said, “that the doctors of the law have written nothing of value concerning presumptions; nor is the subject-matter such as to be reduced within the prescribed limit of any certain rules.  In truth, it is from the actual existing case, and from the circumstances of the persons and of the business, that we ought (under the guidance of an incorrupt judgment of the mind, which is called an equitable discretion) to determine what presumptions or conjectural proofs are to be admitted as rational or rejected as false, or on which the understanding can pronounce nothing, either the one way or the other.”

It is certain, that, whatever over-strictness is to be found in the older writers on this law with regard to evidence, it chiefly related to the mere competency of witnesses; yet even here the rigor of the Roman lawyers relaxed on the necessity of the case.  Persons who kept houses of ill-fame were with them incompetent witnesses; yet among the maxims of that law the rule is well known of Testes lupanares in re lupanari.

In ordinary cases, they require two witnesses to prove a fact; and therefore they held, “that, if there be but one witness, and no probable grounds of presumption of some kind (nulla argumenta), that one witness is by no means to be heard”; and it is not inelegantly said in that case, Non jus deficit, sed probatio, “The failure is not in the law, but in the proof.”  But if other grounds of presumption appear, one witness is to be heard:  “for it is not necessary that one crime should be established by one sort of