On the general head of Evidence, or Proof, your Committee finds that much has been written by persons learned in the Roman law, particularly in modern times,--and that many attempts have been made to reduce to rules the principles of evidence or proof, a matter which by its very nature seems incapable of that simplicity, precision, and generality which are necessary to supply the matter or to give the form to a rule of law. Much learning has been employed on the doctrine of indications and presumptions in their books,--far more than is to be found in our law. Very subtle disquisitions were made on all matters of jurisprudence in the times of the classical Civil Law, by the followers of the Stoic school.[42] In the modern school of the same law, the same course was taken by Bartolus, Baldus, and the Civilians who followed them, before the complete revival of literature.[43] All the discussions to be found in those voluminous writings furnish undoubtedly an useful exercise to the mind, by methodizing the various forms in which one set of facts or collection of facts, or the qualities or demeanor of persons, reciprocally influence each other; and by this course of juridical discipline they add to the readiness and sagacity of those who are called to plead or to judge. But as human affairs and human actions are not of a metaphysical nature, but the subject is concrete, complex, and moral, they cannot be subjected (without exceptions which reduce it almost to nothing) to any certain rule. Their rules with regard to competence were many and strict, and our lawyers have mentioned it to their reproach. "The Civilians," it has been observed, "differ in nothing more than admitting evidence; for they reject _histriones_, &c., and whole tribes of people."[44] But this extreme rigor as to competency, rejected by our law, is not found to extend to the _genus_ of evidence, but only to a particular _species_,--personal witnesses. Indeed, after all their efforts to fix these things by positive and inflexible maxims, the best Roman lawyers, in their best ages, were obliged to confess that every case of evidence rather formed its own rule than that any rule could be adapted to every case. The best opinions, however, seem to have reduced the admissibility of witnesses to a few heads. "For if," said Callistratus, in a passage preserved to us in the Digest, "the testimony is free from suspicion, either on account of the quality of the _person_, namely, that he is in a reputable situation, or for _cause_, that is to say, that the testimony given is not for reward nor favor nor for enmity, such a witness is admissible." This first description goes to _competence_, between which and _credit_ Lord Hardwicke justly says the discrimination is very nice. The other part of the text shows their anxiety to reduce credibility itself to a fixed rule. It proceeds, therefore,--"His Sacred Majesty, Hadrian, issued a rescript to Vivius Varus, Lieutenant of Cilicia, to