I think that you'll find that all truth is exclusive, not inclusive. For something to be true, it means that the opposite of it isn't true, thats exclusive. For someone to say, that all t-shirts are cool, that exclusive because it means also at the same time that all t-shirts can't be not cool.
Every major religion in the world is exclusive in some ways or another.
Christianity, obviously claims that the only name under which men can be saved is the name of Jesus.
Islam: Claims Allah is the one true God and Muhammad is his prophet.
Hinduism: Claims that there is not one way to heaven but reincarnation and karma that determines how many lifetimes you have before their concept of "heaven."
Buddhism: was started by rejecting the tenets of Hinduism and the caste system. (excludes some Hindu beliefs)
Ba'haism: The most inclusive religion in the world and becomes exclusive by excluding the exlusivists.
This concept is known as the law of non contradiction, meaning that if something is true, its opposite cannot also be true.
This is significant because a lot of people are looking for the all inclusive truth, and it doesn't exist because it can't its not intrinsically possible (another way of saying its not within the realm of possibility.)
I believe that for us to live consistently we must think through our beliefs to their logical conclusion so that we don't end up believing contradictory things and then have our world view shattered when someone comes along and challenges what could be fallible and incorrect assumptions.
I would like to state an alternate means of looking at these same issues, maybe not a popular one in this day and cultural age, but unpopularity doesn't discount an idea from being true anymore than popularity assures truth.
I think that it can be said that
1. The bible is true, it makes this claim of itself and also claims to be God-breathed. (If we don't agree on this point, thats ok, but it does throw a wrench in our starting points on this discussion.)
2. If the bible is true, it cannot also be not true (law of non contradiction.)
3. Things not included in the bible or from other cultures, religions etc. may be true or contain truth in them.
4. For things to be true and their converse to not be true, there must be a measuring stick to determine if they are true or not. I would suggest the Bible would be this measuring stick from point 1.
5. With point 3 being the case and assuming it might be true, we can safely say that things from other cultures etc. (I'm not listing a lot but this could mean everything else not in the bible, so tons of things) contain truth as in accordance with the measure of truth (bible) and be very adept at revealing, displaying, painting a picture of the truth or aspects of it. They don't define it because they can't, because certain aspects of the "everything else" would come into contradiction of the measure and they can't both be true.