Torture.
The first question to ask yourself is what is your position or perspective on the topic. You may not think it very necessary to consider the merits of torture because there is clearly only one "correct" position to hold and that every decent individual would hold such a position.
Most governments indicate publically that they are opposed to torture. They sign International Treaties or agreements which say they won't engage in the practice. Many such governments engage in torture.
Why do governments engage in torture. In some countries torture is regularly used to extract confessions for everyday crimes. In Canada, the state makes this practice by its officials more difficult by refusing to let its paid prosecutors to enter statements in criminal trials with out a "voir dire" - a trial within a trial to determine that the statement was not secured by way of torture. That is that the statement was voluntarily given without coercion or bribe.
Some countries torture to get rid of political dissent, silent critics and perceived security threats. Their perspective is that it is better to cause pain to a certain portion of the population for the sake of the peace, stability and well being of the greater number. After all all nations agree that it is acceptable to kill some in order to protect your way of life and life itself. This is what war and having solders is all about. Surely taking a "lesser" measure such as causing other mental or physical pain is at the very least, the lesser evil
Some countries torture in response to terrorist threats. Lives of innocent lives may be saved. After all a nuclear bomb was dropped on cities with populations in excess of a million with the justification that more lives and suffering would be averted.
History of Torture
In ancient Greece and Rome only slaves and foreigners could be tortured except in cases of treason. From the 12th century on civil law justice systems developed that required circumstantial evidence of a crime known as indicia before an accused could be interrogated. But to be convicted required either two witnesses or a confession- hence torture became the primary basis for conviction.
In 1764 Cesare Beccaria wrote a On Crimes and Punishment which denounced torture:
Torture "is a sure route for the acquittal of robust ruffians and the conviction of weal innocent."
This direct simple pamphlet became a best seller through out Europe and turned the tide on torture.
In England the court systems did not permit torture but during the Star Chamber established by the Crown and outside the court system permitted torture from 1487 until its abolition in 1640.
Torture as a tool for state security continued into the 20 century. Following the atrocities of the Nazi Torture chambers torture was absolutely banned in the 1948 Universal Declaration of Human Rights . The Geneva Convention of 1949 banned "mutilation, cruel treatment and torture of prisoners"
References
Beccaria, Cesare. (1764). On Crimes and Punishment
Eds Roth, Kenneth, Minky Worden (2005) Torture, Does It Make Us Safer? Is It Ever OK? A Human Rights Perspective