The legal conception of duress, originally so narrow as to apply only to cases of imprisonment or serious violence to the person, or threats of such imprisonment or violence,2 has gradually expanded under the influence of equity, until it is now commonly said to consist of any actual or threatened unlawful exercise of power possessed, or believed to be possessed, by one party over the person or property of another, from which the latter has no other means of immediate relief than the performing of the required act.1 Indeed it is becoming increasingly difficult, because of the adoption of equitable doctrines in common law courts and the confusion, in many jurisdictions, of legal and equitable procedure, to distinguish duress from what in equity is called undue influence.2 But it is unnecessary here to attempt a very precise definition of the bounds of either. It need only be said that upon principle any species of compulsion that would make a contract voidable, either at law or in equity, should be enough to support an action to recover the value of a benefit conferred thereunder. Sec. 213. (II) Sundry instances of obligation classified according to means of compulsion employed. - The cases in which restitution is most commonly sought may be classified, according to the means of compulsion employed, as follows:

1 Koenig v. People's Gas, etc., Co., 1910, 153 111. App. 432. 2 Skeate v. Beale, 1841, 11 Ad. & El. 983.

(1) Violence to the person or imprisonment - commonly called duress of person.

(2) Threat of legal proceedings.

(3) Seizure or detention of personal property - commonly called duress of goods.

(4) Assertion of fictitious lien on real property or refusal to discharge valid lien.

(5) Injury to business.

(6) Oppressive refusal to discharge a duty.

(7) Oppressive refusal to loan money at a legal rate of interest.

They will be considered in the above order.