The prohibition of torture is a peremptory norm in public international law – meaning that it is forbidden under all circumstances – as well as being forbidden by international treaties such as the United Nations Convention Against Torture . It is generally agreed that torture is inherently morally wrong because all forms of torture "involve the intentional infliction of extreme physical suffering on some non-consenting and defenceless person", although it does not necessarily follow that torture is wrong in all circumstances. In practice, torture has been employed by many or most prisons, police and intelligence agencies throughout the world. Philosophers are divided on whether torture is forbidden under all circumstances or whether it may be justified in one-off situations, but without legalization or institutionalization.