There is no evidence that the precordial thump improves recovery in unwitnessed cardiac arrest. Various evidential verb forms exist to express unwitnessed, retold, and doubtful action. The inferential mood is used to report unwitnessed events without confirming them. Prior to that time, an unwitnessed exchange of marriage vows was deplored but valid. Suggested causes include poison, "exposure and privation", or simply "strange and unwitnessed circumstances". The League was a "publicist for Jacobitism on a scale unwitnessed since the eighteenth century".