Legal standards of conduct appear first in Roman equity. In certain cases of transactions or relations involving good faith, the formula was made to read that the defendant was to be condemned to that which in good faith he ought to give or do for or render to the plaintiff. Thus the judge had a margin of discretion to determine what good faith called for and in Cicero's time the greatest lawyer of the day thought these _actiones bonae fidei_ required a strong judge because of the dangerous power which they allowed him. From this procedural device, Roman lawyers worked out certain standards or measures of conduct, such as what an upright and diligent head of a family would do, or the way in which a prudent and diligent husbandman would use his land. In similar fashion English equity worked out a standard of fair conduct on the part of a fiduciary. Later the Anglo-American law of torts worked out, as a measure for those who are pursuing some affirmative course of conduct, the standard of what a reasonable, prudent man would do under the circumstances. Also the law of public utilities worked out standards of reasonable service, reasonable facilities, reasonable incidents of the service and the like. In all these cases the rule is that the conduct of one who acts must come up to the requirements of the standard. Yet the significant thing is not the fixed rule but the margin of discretion involved in the standard and its regard for the circumstances of the individual case. For three characteristics may be seen in legal standards: (1) They all involve a certain moral judgment upon conduct. It is to be "fair," or "conscientious," or "reasonable," or "prudent," or "diligent." (2) They do not call for exact legal knowledge exactly applied, but for common sense about common things or trained intuition about things outside of everyone's experience. (3) They are not formulated absolutely and given an exact content, either by legislation or by judicial decision, but are relative to times and places and circumstances and are to be applied with reference to the facts of the case in hand. They recognize that within the bounds fixed each case is to a certain extent unique. In the reaction from equity and natural law, and particularly in the nineteenth century, these standards were distrusted. Lord Camden's saying that the discretion of a judge was "the law of tyrants," that it was different in different men, was "casual" and dependent upon temperament, has in it the whole spirit of the maturity of law. American state courts sought to turn the principles by which the chancellors were wont to exercise their discretion into hard and fast rules of jurisdiction. They sought to reduce the standard of reasonable care to a set of hard and fast rules. If one crossed a railroad, he must "stop, look and listen." It was negligence _per se_ to get on or off a moving car, to have part of the body protruding from a railroad car, and the like. Also they