The right not to be tortured is unique among internationally recognised human rights.
Where even the right to life is qualified by exclusions - in war, in self-defence, or in judicial proceedings where capital punishment is legal - the right not to be tortured stands as an unconditional and unqualified right.
And yet, as J. Jeremy Wisnewski and R.D. Emerick point out in their clear and eloquent book, The Ethics of Torture, there is no chapter of human history, including our own, that has been without it.
As far as academic discussion is concerned, the unconditional status of the ban on torture has attracted challenge from a number of perspectives. Utilitarians in particular are reluctant to recognise any absolute moral prohibitions.
In one philosopher's admittedly improbable scenario: what should you do if a terrorist is about to explode a bomb that will kill everyone in the world unless you agree to publicly torture your mother to death? Today, the necessity of saving the world might seem to trump the personal moral challenge, although an earlier writer, William James, in a similar example, had reached a different conclusion: if millions of people could be "kept permanently happy on the one simple condition that a certain lost soul on the far-off edge of things should lead a life of lonely torment", such a bargain would, James believed, strike ordinary people as so hideous that they would reject the chance to clutch at the prospect of universal happiness.
Wisnewski and Emerick, however, are writing in a new era when the nature of threats are such that there are in the Western democracies people in influential positions who are ready openly to defend torture when they judge it to be the only way to save innocent people from injury or death.
The authors themselves, however, regard the use of torture as a means to desired ends as always morally impermissible.
They recognise, nevertheless, that much may depend on competing definitions of the practice, some of which, as they observe, have been far from disinterested.
They themselves eschew any attempt to capture all the dimensions of torture in a single definition, offering instead some broad headings that include the judicial torture that characterised the witch trials of the 17th century, the use of torture as punishment or as an interrogation technique, and the use of deliberately dehumanising techniques aimed at destroying a person's own self-image.
The authors see the UN Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, according to which torture is the formally sanctioned infliction of pain to obtain information or a confession, as deficient in two ways. First, because private torture, such as that by criminals or sadists, is still torture though lacking formal sanction. Second, because there are many examples of coercive violence that are not covered by the definition and would-be torturers would simply use, as the authors put it, their "malicious creativity" to find new techniques to avoid the prohibition.
And so the authors focus on the position of those who believe torture could be legally permitted or at least morally justified in certain circumstances.
They reject the suggestion that officially issued "torture warrants" would limit the use of torture and argue that this would be a breach of the UN Convention. They also reject the suggestion that it sometimes may be morally permissible and the accompanying argument that to reject this is to place one's own moral rectitude above the lives of others.
The basis of their own position is a commitment to the Kantian principle of respect for persons and a generalised objection to thought experiments of the "ticking bomb" variety, which, they say, depend on an inadequate understanding of torture.
The Ethics of Torture is a clear and informative book. It offers a succinct appraisal of the arguments surrounding torture and is all the better for having an acknowledged point of view on what has become a central issue for Western nations facing the challenge of how to respond to terrorist threats to their own security.
The Ethics of Torture
By J. Jeremy Wisnewski and R.D. Emerick. Continuum, 176pp. £60.00 and £16.99. ISBN 9780826498892 and 8908. Published 4 June 2009