a temporary principle put forth in order to help in reducing our knowledge to system. A hypothesis, as such, is a temporary explanation of a phenomenon, and is subject to certain conditions—1. The fact for the explanation of which the hypothesis is framed must be known to be a fact. 2. Before any one hypothesis be resorted to, it must be ascertained that no other hypothesis will answer equally well with the one chosen. The value of a hypothesis depends—1st, on its internal consistency, and external accordance with things known to be true; 2d, on the completeness with which it explains the phenomena in question; and 3d, on the extent to which it is independent of other hypotheses.