The existence and nature of truth is indeed vital. To the Muslims credit, they are not moral relativists. The progressive socialists lay claim to that. The Muslims are kind of like “Sola Scriptua” on steroids. They believe the Koran is true even though it is admitted that it appears to contradicted by physics, archeology and other histories, appears to be muddled and even self-contradictory, and appears to say things that are illogical.
“Sola Scriptura” is the doctrine that “only” the Bible is a reliable source of truth. On its face, this is ridiculous as inference from the necessarily limited number of statements in the Bible to the potentially unlimited number of statements that are possibly true requires logic. Yet, according to this doctrine, only the Bible and not logic is reliable.
We can say that, with the Enlightenment, we came to embrace the scientific method. That the most reliable source of truth is when faith and reason come together. Not that everything that is true can be put to a scientific test. But, enough things that are true can be so tested that we can have confidence in the untestable contentions in a source that claims to reveal truth.
So, let’s consider the Koran. It is claimed to be the dictated word of God, literally true from the beginning of time and for all time. O.K., consider its statement that the world is flat. This would be an amazing thing if it were true, because all educated people have known that the world is a globe since the time of the Egyptians and the Greeks. If we put this amazing assertion to the test, and found that in spite of the apparent curvature careful measurement indicates, the world really is flat, then we could have some confidence in other statements in the Koran that are not testable.
By the way, the argument that the Bible says or the Christian community used to believe the world is flat is fake. It was promoted by critics of Christianity during the 19th Century and eventually the joke became the truth. Much like Democrats believe Sarah Palin said she could see Russia from her house.