Necessity is a legal defense that justifies a defendant's unlawful actions when those actions are taken to prevent a greater harm from occurring. This concept often arises in cases involving drug offenses, where individuals may argue that their illegal activities were necessary to avert an imminent danger or threat, such as protecting themselves or others from harm. The principle of necessity emphasizes the importance of weighing the consequences of actions and determining whether breaking the law was the only viable option to address a critical situation.