With the horrific ISIS-led attacks in Paris, the debate has once again risen about whether Islam is a religion of peace or a religion that promotes violence. 

People on both sides of the debate often express a moral certitude about their position. But really, is there any way to know with certainty?  

For instance, can one point to a definitive authority to settle the question? 

Not really. Islam does not have an official magisterium, i.e., a universal teaching authority to which one can point for THE true interpretation of Islam. Like every other world religion, Muslims have a tradition that contains different schools and strands of scholarly interpretation, and there is really no surefire way to determine which of these strands has a more authoritative understanding of Islam than the others. Roman Catholics typically consider themselves as having the gold standard for a centralized authority, which consists of the bishops with the pope as their head. But even Catholics have their various schools of thought and interpretation, in addition to debates about which teachings are truly binding.   

Can one point to the belief and practice of a majority of Muslims?

Not necessarily. The fact that something is the belief and practice of the majority is no evidence of its veracity. The philosopher Bertrand Russell put it more strongly: “The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd.” In history, there are plenty of examples when the majority of people were considered by future generations to be in wrong.  

Just some questions at this point. I don’t necessarily believe that it’s illegitimate to claim “Islam is a religion of peace,” or its opposite. But seriously, how can people know with certainty?