Title I, Of that primary dignity of the law, certainty

VIII. Certainty is so essential to a law, that a law without it cannot be just; for if the trumpet gives an uncertain sound, who shall prepare himself to the battle? So if the law has an uncertain sense, who shall obey it? A law, therefore, ought to give warning before it strikes: and it is a true maxim, that the best law leaves least to the breast of the judge; which is effected by certainty.

IX. Laws have two uncertainties—the one where no law is prescribed, the other when a law is ambiguous and obscure; wherefore we must first speak of cases omitted by the law, that in these also may be found some rules of certainty.