The very idea of the law in a constitutional republic involves the requisite that it be a rule, a guide, uniform, fixed and equal, for all, till changed by the same high political power which made it. This is what entitles it to its sovereign weight.
Juries must, of necessity, be governed, in reaching many results through inferences from other facts, by certain laws of nature and human reason. They are often obliged to infer one thing from another, and this, whether that other be a fact direct or circumstantial.