Though the common law distinguished duress and menace, or as it was later phrased duress by imprisonment and duress by threats, there is no logical distinction worth preserving. Imprisonment operates as a means of coercion only because of its threatened continuance, and there seems no material difference between a threat whether express or implied to continue an existing imprisonment, and a threat to arrest and imprison one who is then at large, provided the threat is accompanied with apparent ability to execute it. Whether threatened imprisonment is immediately imminent or not, involves a distinction of degree rather than of kind.