Comparing religions is never easy. As a start, one must be immersed well in both of the religions involved in the conversation. And, considering that religion entails belief, is it really possible to understand a religion from the outside? Hence it would be really easy to caricature and misrepresent another religion. Nevertheless, one can still try. And I think the most important principle to do so is to realize that each religion has its own categories and vocabularies. Failure to realize this will result in a bad misunderstanding.
For example, didn’t Muhammad misunderstand what did it mean by the Gospel? Sura 3.48 reads as follow, “And He [the Moslem god] will teach him [Jesus] writing and wisdom and the Torah and the Gospel.” Here the Gospel is construed to be similar with the Torah and other writings. And, since the Torah was assumed to be a book given to Moses, then the Gospel means a book given to Jesus. And I believe the majority of Moslems have believed this way. Gospel means a book that the Moslem god has given to Jesus, similar to Torah which he gave to Moses, or Qur’an which he gave to Muhammad.
While, on the other hand, the Christians has never thought of the Gospel in this way. So here we have an example of how a technical word can mean differently in two religions. Indeed, Muhammad didn’t necessarily have to have misunderstood the word. It could just simply means that for Christians and for Moslems, ‘Gospel’ has a different meaning.
To realize this means we should clarify first what does a word signify when we converse with adherents of other religions. What does it mean when we say ‘the Gospel’? What does it mean when we say ‘salvation’? Indeed, does ‘salvation’ matter on the other side? Only then an interfaith dialogue can be genuinely conducted.