When a legal rule is set forth, it usually describes real-world events and says, there’s a consequence, such as a right of action (or a criminal act, or a right to compensation) which follows if these real-world events are present. As all lawyers know, of course, such statements of rules don’t mean exactly what they say. Real-world events that aren’t described in the rule may come to be treated as if they are within the rule, because the courts feel that the not-mentioned items satisfy all the same purposes as the listed items do, when the overall purposes of the rule are considered. Similarly, real-world events which a layman would think are covered by the rule often are “read out” of the rule, as not within the draftsmen’s “intent” etc. All this makes sense, in that rules are an approximation of goals to be reached.
Wendy J. Gordon, Notes on Property Themes/Scholarly Methodology (1985).