If religion indeed suffers from some sever cases of internal inconsistency, this means that one shall have to find significant changes in religious arguments and beliefs as time passes by.
History shows us that this is true. Religious claims have always shifted (or tried to shift) to ideas that were more likely to be accepted by the masses, or were impossible to avoid. One good example is an economical one, and that is the rate of interest. Before the tenth century, Scholastic thinkers strongly prohibited any interest based on religious beliefs. But the progress of market economy is actually based on interest, and when throughout time to 14th and 15th century markets started to become more and more completed, interest became essential for economic growth. With advanced banking system in Florence, prohibition of interest effectively ended.
Nowadays you can see the same process through Islamic countries. Also, you can see this process for many other things as well; of course one good example is again the progress of tolerance for Homosexuality. One more interesting religious idea-shift is its attitude towards racism. Before, religion was the advocate of slavery and discrimination against black men and women, but in the 60s Martin Luther King (who himself was a Baptist minister) turned it into a weapon against discrimination.
We can find many examples of this sort, and I do not think that religious people will disagree that we do have these shifts of ideas in religious beliefs. But what can be said in defense of religion? One thing comes into my mind, and I have heard this quite a lot from Islamic apologists in the case of these ‘shifts’: “It was not Islam that was wrong, it was us.” Or “It was our lack of understanding of Koran; otherwise we know that it cannot be wrong.”
This answer only ‘seems’ right, because now we can see that it faces a strong and yet simple dilemma and I think we could call it the ‘dilemma of the book of Thoth’.
Thoth was (or is?!) the mythological Egyptian god of wisdom and he had written a book that contained all his knowledge about the world and the gods themselves. If somebody could read ‘the book’, he or she would have been capable of knowing every secret of the known world and even could literally see the gods themselves. Neferkaptah, an Egyptian prince, read the book and became almost a god. That was why the gods punished him by killing his son and wife: They didn’t want a human to possess such power. Neferkaptah later committed suicide and was buried with the book to guard it forever.
Now, what has this little mythological story got to do with our argument? It’s simple: These so called ‘holy books’ of ours (The Koran, The Bible, and The Torah) are either utterly wrong, or they are not understandable. They are not like the book of Thoth, that was (or is) written by a god and when you read it you can see the effect immediately. When you read any of those books, you will see that your ‘knowledge’ has not increased; they only abuse what you already know. They are exactly like mediums: vagueness is what they are made of. This is what makes religious books and mediums equally fake.
And that is the key to those shifts in religious ideas. Scientific theories change because they are based on scientific facts and other theories, and they were never supposed to be absolutely true to begin with. We already know this from David Hume. Religious ideas change because they become internally inconsistent (and because they were made up to begin with).
Religious people cannot believe that their holy book is false; if they do, they are not religious any more. At first look it seems plausible for them to doubt their own understanding. But In that case, how on earth they dare saying “We know the truth.”?! How dare Catholics condemn Homosexuality and say “because God says so”. You don’t even understand your God! And Muslims are the worst; at least Christianity has had a renaissance, Islam still holds a great power over people’s minds.
The worst result of the vagueness of these books is that they can justify almost ‘anything’. They justify sexism in the Middle East, and yet in the same place you can find devoted Muslims that say “this is NOT what the Koran says.” They justify killing gay men and women, and recently I have seen articles, written by believers about how the Bible and the Koran “do NOT condemn homosexuality.”
Right now Islamist extremists are after nuclear weapons in Iran, but in the meantime mullahs say the world that Islam prohibits making weapons of mass destruction. Now, we can trust them, right?!