Interpretation of law determined by courts (judges and juries)
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The sentence of the judge is to be taken as the application of the law of nature to a specific case.
The interpretation of the law of nature is the sentence of the judge constituted by the sovereign authority to hear and determine such controversies as depend thereon, and consisteth in the application of the law to the present case. For in the act of judicature the judge doth no more but consider whether the demand of the party be consonant to natural reason and equity; and the sentence he giveth is therefore the interpretation of the law of nature; which interpretation is authentic, not because it is his private sentence, but because he giveth it by authority of the sovereign, whereby it becomes the sovereign's sentence; which is law for that time to the parties pleading.
Hobbes, Lev XXVI 23
The law as applied to a particular case is determined (perhaps fixed) by a judge.
If therefore a man have a question of injury, depending on the law of nature; that is to say, on common equity; the sentence of the judge, that by commission hath authority to take cognizance of such causes, is a sufficient verification of the law of nature in that individual case. For though the advice of one that professeth the study of the law be useful for the avoiding of contention, yet it is but advice: it is the judge must tell men what is law, upon the hearing of the controversy.
Hobbes, Lev XXVI 17
Argument and example
Judges need not study the law.
The abilities required in a good interpreter of the law, that is to say, in a good judge, are not the same with those of an advocate; namely, the study of the laws. For a judge, as he ought to take notice of the fact from none but the witnesses, so also he ought to take notice of the law from nothing but the statutes and constitutions of the sovereign, alleged in the pleading, or declared to him by some that have authority from the sovereign power to declare them; and need not take care beforehand what he shall judge; for it shall be given him what he shall say concerning the fact, by witnesses; and what he shall say in point of law, from those that shall in their pleadings show it, and by authority interpret it upon the place. The Lords of Parliament in England were judges, and most difficult causes have been heard and determined by them; yet few of them were much versed in the study of the laws, and fewer had made profession of them; and though they consulted with lawyers that were appointed to be present there for that purpose, yet they alone had the authority of giving sentence...
Hobbes, Lev XXVI 27