Why the Bible and the Koran are not Manuals for today

How can anyone point to the Koran or the Bible and say these documents are the bedrock of a peaceful and humane religion?  (This may apply equally to other holy scriptures but I am less familiar with them, so let's stick to these two).  They are full of blood-curdling violence and attitudes that would be completely unacceptable if they were promoted today.   But their violence and anachronistic attitudes are not at all surprising; they were written by people who were ignorant about the world around them, when science as we know it today did not exist, when human life was cheap and hung by a thread, threatened by hunger, natural disaster and disease, where people attacked and murdered each other over food and water as well as the gods they worshipped.  Even the concept of written knowledge was pretty much unknown, other than amongst a few educated elite (and they did not include The Prophet Muhammed, apparently).

So when Saint Paul espouses slavery, or The Prophet wields his bloody sword, or women are treated as chattels, we should not get too hung up about it.  That was then, and this is now.  What the authors of these sacred texts thought 1300 or 2000 years ago is irrelevant to our lives today.  Sure, they have contributed to the intellectual development of the human race, and are interesting from an historical perspective, but as a species we moved on.  We have learned to order our societies better, to control our environment so that life became safer and in doing so we have created time and space to become more tolerant of each other and show empathy for other human beings.  We replaced ignorance and superstition with science and intellect.

To rely on The Bible or the Koran to inform your behaviour is to say that you believe the world in which they were created is a better place than the one you live in today.  Some people may think so; the real fundamentalists.  I think there are even people who believe the world is flat.  But I don't see them rushing to live without clean running water, modern medicine, the written word, (almost) universal literacy, electronic communications or even ready meals.   They do not yearn to live in a time when you existed every day with simple fear that your life might be extinguished tomorrow by a wild animal, a microbe the tribe down the valley or some incomprehensible natural disaster.  

I am not saying you should not live without belief though.  You can believe in the inherent good nature of (most of) humanity; that we know what ethical behaviour is, without recourse to "the good book", and (most people) usually display it. You can believe that an enquiring mind is always better than a closed one.  Of course some people have thoughts that are dangerous to the people around them, or to sections of society, or to humanity as a whole.  To those we show a healthy scepticism.  But approach other ideas with an enquiring and scientific mind and the ascent of mankind will continue unabated, albeit with some hiccups on the way, even further from the distant and irrelevant world to which the Bible and Koran relate.

Some believers will counter by saying that there are lots of good bits in the Bible that they find help them to feel their way in the world.  Some say that the Koran guides them to a pacific way of life.  But if you seriously believe these books have some authority beyond anything else in your local bookshop, then you cannot pick and choose.  You cannot deny the violence, inhumanity, the unacceptable side of them and you cannot rationally argue with anyone who chooses to use that unacceptable side as the basis of their own personal beliefs.