Discuss with reference to time-barred debts and irrecoverability of voluntary payments.

Duty, liability, obligation — the three words orbit each other in every jurisprudence course. This unit isolates obigation as the jurists' term for the binding legal relation itself: the word descends from the Latin obligatio, from ob-ligare — to bind to, to tie fast. Roman lawyers pictured it as a literal chain: the debtor was bound to the creditor, and performance or satisfaction severed the chain. Modern law has humane the picture but kept the idea — an obligation is a legal bond by which one person (the obligor) is bound to render a performance (to act, to deliver, to pay, or to forbear) in favour of another (the obligee). Salmond located obligations among the archetypal legal relations; Austin treated obligation as the hallmark of a command ("being bound or obnoxious to a sanction"); Hart's critique of Austin — the gunman who orders your wallet creates being obliged (a prediction of harm) but not an obligation (a normative reason) — remains the classic analytical contrast.