A short while back somebody commented on Facebook that somebody [else] had quoted the Quran in a forum devoted to discussing Christian issues. This seemed to the commentator to be the camel’s nose under the tent, possibly the first step in an electronic Jihad or something. This, we felt, was silly in more ways than one, especially in a discussion on matters relating to the natural law “written in the hearts of all men.”
Frankly, the natural law is the one place where ecumenism and true interfaith dialog can really take place. All you have to do is keep in mind the different roles of faith and reason. All religions can agree on matters based on reason and discernment of the natural law. So can atheists, for that matter. The natural law is based on our observations concerning human nature and what humanity has, in all times and places, considered “good.” (We won't get into the deviations; Aristotle handles the case of when people think something that is evil is good, but let's stick to the main point.)
Where the different faiths and philosophies differ in matters of natural law is in the application thereof. For example, “murder” and “theft” have always and everywhere been regarded as evil. Is human sacrifice, however, murder? Is stealing or redistributing wealth when some are deemed to have “too much” theft?
Restrict interfaith dialogue to this sort of thing, and a great deal can be accomplished. This is especially so among the three great Abrahamic religions. Thus, in matters relating to the natural law, all faiths and philosophies can find value in others as different expressions of truth.
It’s when we get into matters of faith that the trouble starts. Faith is based on our willingness to believe and is not based on reason. It does not and cannot contradict reason, of course, and faith and reason complement and support each other, but you cannot subject matters of faith to the same process as matters of reason. They cannot be proved either inductively or deductively.
The recent (i.e., over the last 300 years or so) history of thought reveals an extremely disturbing trend, however. More and more matters that pertain to reason are based on faith, and matters that pertain to faith are rejected because they are not susceptible of proof. As Mortimer Adler put it, people have confused knowledge (which is always true) with opinion (which may or may not be true), and reason has come out the loser.
For example, I have a friend who publishes occasional papers periodically. Usually these attract about as much attention as my books. Recently, however, he came out “against” the theory of evolution of religious grounds. People actually took notice of this and posted comments.
Why waste your time? As far as the Catholic Church or any other religion is concerned, whether the theory of evolution is true or false is completely irrelevant. God made the world and everything in it. How He did so is a nice intellectual point, but, ultimately, whether Genesis is literally true, or whether we are to take it metaphorically or mythically (in the good sense), makes no difference. The problem the Catholic Church has with evolution is not with evolution, but with those learned and semi-learned dolts who insist that because evolution is “true” (actually, it has not been proved in scientific terms), then the account in Genesis is not literally true, and therefore God does not exist (and similar arguments).
Bull. Any honest atheist could pick out the many logical flaws in such arguments, e.g., how can you prove or disprove the existence or non-existence of an immaterial Being by material means?
So, as long as the cites from the Quran or any other holy book — or any book, for that matter — are consistent with reason, there is no reason why Catholics or anyone else cannot use them with profit. You should, however, be sound enough in the precepts of your own faith to be able to discern what is good in others without endangering your own.