It should be observed that the subject of inquiry is matter of fact, and not of abstract mathematical truth. The latter alone is susceptible of that high degree of proof, usually termed demonstration, which excludes the possibility of error, and which therefore may reasonably be required in support of every mathematical deduction. But the proof of matters of fact rests upon moral evidence alone; by which is meant not merely that species of evidence which is employed in cases respecting moral conduct, but all the evidence which we do not obtain either from our own senses, from intuition, or from demonstration. In the ordinary affairs of life we do not require nor expect demonstrative evidence, because it is inconsistent with the nature of matters of fact, and to insist on its production would be unreasonable and absurd. And it makes no difference, whether the facts to be proved relate to this life or to the next, the nature of the evidence required being in both cases the same. The error of the sceptic consists in pretending or supposing that there is a difference in the nature of the evidence, where there is no difference in the nature of the things to be proved; and in demanding demonstrative evidence concerning things which are not susceptible of any other than moral evidence alone, and of which the utmost that can be said is that there is no reasonable doubt of their truth.(48) § 27. In proceeding to weigh the evidence of any proposition of fact, the previous question to be determined is, _when_ may it be said to be proved? The answer to this question is furnished by another rule of municipal law, which may be thus stated:— _A proposition of fact is proved, when its truth is established by competent and satisfactory evidence._