A state of affairs is necessary if it has to be the case. Logical necessity is a product of the law of noncontradiction. Causal necessity, it has been thought, is a different form of necessity.
A situation that compels an act because of some need; can provide grounds for an affirmative defense. See full article titled Defenses of Necessity and Choice of Lesser Evils
A person is excused from criminal liability where he acts in an emergency to protect life, health or property in a reasonable way and with no acceptable alternative. The law will excuse the commission of a lesser evil to avoid a greater evil when there are no other peaceful, effective alternative remedies open. The circumstances in which this defence might apply cannot be defined beforehand.
The whole of all physical and biological laws which govern the matter in every form and expression. liberty is the contrary.
A legal defense that is similar to self-defense and duress because it excuses an otherwise criminal act when committed to avoid a greater harm.
In criminal law, necessity may be either a possible excuse or an exculpation for breaking the law. Defendants seeking to rely on this defense argue that they should not be held liable for their actions as a crime because their conduct was necessary to prevent some greater harm. For example, a drunk driver might contend that he drove his car to get away from an armed robber.
In tort common law, the defense of necessity gives the state or an individual a privilege to take or use the property of another. A defendant typically invokes the defense of necessity only against the intentional torts of trespass to chattels, trespass to land, or conversion. The Latin phrase from common law is necessitas inducit privilegium quod jura privata, "Necessity induces a privilege because of a private right."