An inference as to the existence of one fact, from the existence of some other fact, founded on a previous experience of their connexion. Or it, is an opinion, which circumstances, give rise to, relative to a matter of fact, which they are supposed to attend. To constitute such a presumption, a previous experience of the connection between the known and inferred facts is essential, of such a nature that as soon as the existence of the one is established, admitted or assumed, an inference as to the existence of the other arises, independently of any reasoning upon the subject. It follows that an inference may be certain or not certain, but merely, probable, and therefore capable of being rebutted by contrary proof. In general a presumption is more or less strong according as the fact presumed is a necessary, usual or infrequent consequence of the fact or facts seen, known, or proven.
Presumptions are either legal and artificial, or natural.
Legal or artificial presumptions are such as derive from the law a technical or artificial, operation and effect, beyond their mere natural. An example of another nature is given under this head by the civilians. If a mother and her infant at the breast perish in the same conflagration, the law presumes that the mother survived, and that the infant perished first, on account of its weakness, and on this ground the succession belongs to the heirs of the mother.