23. But when there is some controversy of the fact itself, to wit, whether that be done or not which is said to be done, the natural law wills that the arbiter trust both parties alike, that is, because they affirm contradictories, that he believe neither. He must therefore give credit to a third, or a third and fourth, or more, that he may be able to give judgment of the fact, as often as by other signs he cannot come to the knowledge of it. The eighteenth law of nature therefore enjoins arbiters and judges of fact, _that where firm and certain signs of the fact appear not, there they rule their sentence by such witnesses as seem to be indifferent to both parts_. [Sidenote: The nineteenth law, that no contract is to be made with the judge.] 24. From the above declared definition of an arbiter may be furthermore understood, _that no contract or promise must pass between him and the parties whose judge he is appointed, by virtue whereof he may be engaged to speak in favour of either part, nay, or be obliged to judge according to equity, or to pronounce such sentence as he shall truly judge to be equal_. The judge is indeed bound to give such sentence as he shall judge to be equal, by the law of nature recounted in the 15th article: to the obligation of which law nothing can be added by way of compact. Such compact therefore would be in vain. Besides, if giving wrong judgment he should contend for the equity of it, except such compact be of no force, the controversy would remain after judgment given: which is contrary to the constitution of an arbiter, who is so chosen, as both parties have obliged themselves to stand to the judgment which he should pronounce. The law of nature therefore commands the judge to be disengaged, which is its nineteenth precept. [Sidenote: The twentieth law, against gluttony and such things as hinder the use of reason.] 25. Furthermore, forasmuch as the laws of nature are nought else but the dictates of reason; so as, unless a man endeavour to preserve the faculty of right reasoning, he cannot observe the laws of nature; it is manifest, that he who knowingly or willingly doth aught whereby the rational faculty may be destroyed or weakened, he knowingly and willingly breaks the law of nature. For there is no difference between a man who performs not his duty, and him who does such things willingly as make it impossible for him to do it. But they destroy and weaken the reasoning faculty, who do that which disturbs the mind from its natural state; that which most manifestly happens to drunkards, and gluttons. We therefore sin, in the twentieth place, against the law of nature by drunkenness. [Sidenote: The rule by which a man may presently know, whether what he is about to act be against the law of nature or not.]