George Orwell, writing about religious belief in England, commented that what he wanted to know was not how many people confessed to a vague belief in a supreme being but how many believed in Heaven the way they believed in Australia. I was recently reminded of that comment reading a book on Ottoman law. Under that legal system, there were situations in which a defendant could clear himself by swearing an oath. According to the author's account, there were records in the surviving legal documents of capital cases where the defendant refused to swear and was executed as a result, as well as other cases where the defendant was convicted of a capital offense on his own voluntary confession. The obvious conclusion is that the defendant must have believed in Heaven and Hell very much as Orwell's contemporaries believed in Australia, and preferred death with a hope of Heaven to a life leading to Hell.
It is the obvious interpretation, and the one the author of the book I was reading offered. It may well be the correct interpretation. But I would want to know more about the situation to be sure.
Imagine someone a few centuries hence looking at records from the current American legal system without much knowledge of how it actually worked. Observing that a large majority of felony convictions were by confession, he might well conclude that 21st century American criminals were so honest, perhaps so afraid of divine punishment for denying their crimes, that they preferred a certainty of prison to a chance of freedom bought at the cost of a lie. What he would be missing would be the institution of plea bargaining, under which a defendant confesses to a lesser charge in exchange for not being tried on a greater, choosing a certainty of (say) one year in prison over a gamble between going free and serving a much longer sentence. Given that institution, the fact that someone pleads guilty not only does not show that he is honest, it does not even show that he is guilty.
Which makes me wonder whether we might be missing similar features of the Ottoman case. The charges were probably for Hadd offenses, the short list of offenses deemed Koranic. Hadd offenses have fixed penalties and high standards of proof. Zina, unlawful sexual intercourse, is a capital offense if committed by someone who is or has been married and so has had the opportunity for lawful intercourse, but normally requires four witnesses to the same act for conviction. Or confession.
In some, perhaps all, cases the same act that can be prosecuted as a Hadd offense with a fixed penalty and a high standard of proof can also be prosecuted as a Tazir offense with a variable penalty, set by the judge, and a lower standard; the schools of law differ on the upper bound of the penalty. One can imagine a case where a defendant believed that if he denied the Hadd charge he would be tried instead on the Tazir charge and receive a penalty as severe or almost as severe. And one can also imagine pressures, legal or non-legal, religious or secular, that would make him prefer the former alternative.
There is another possibility. Islamic religious law, fiqh, does not permit torture. Ottoman law, a fusion of fiqh and Sultanic pronouncements (kanun), did. So we do not know, at least I do not know, how voluntary the voluntary confessions were.
One might be able to explain away the evidence for strong religious belief along these lines, but it is entirely possible that the author I have been reading is correct in his interpretation. For those of us who do not believe in religion, it is tempting to see other people's belief as only semi-real, as more like my belief in the world of Lord of the Rings (the book, which I read early enough so I had to wait for the second volume to be published, and have reread many times since) than my belief in Australia. It is tempting to interpret our picture of how religious people were in the past as an artifact of filtered data, our sources for the relevant history largely consisting of accounts written by clerics, a point made by Georges Duby, a prominent medieval historian, in a book that used a rare secular source to provide a balancing picture. But it is hard to see how one can give a complete account of history, or even of the present world, without concluding that for a substantial number of people Heaven really was, or is, as real as Australia.