I don't want to get into an argument with anyone on the forum, but I would also like to weight in. The following is my opinion. I am not making it vocal in the hope to persuade anyone to relinquish their own opinion or belief, but to provide an extra perspective on the situation. If it is completely contrary to what you believe, please don't give it a second thought. You are entitled to your opinion just as much as I am.
Leviticus, as stated, is a book in the old testament mainly comprised of rules, laws and punishment. As to who wrote the book, there are two common beliefs. Moses, as I have researched, seems to be the most common believed author. Another opinion is that since Leviticus is a book of priestly rules that perhaps the clergy of the time came together and wrote it.
Either way, it is my personal belief that whoever wrote it, was only one man or one group of men. Over time, society and it's values have changed. I don't believe we can fall back on a book of rules that were written to guide the people of a completely different era. Furthermore, what's to say that whoever did write the book didn't have a personal agenda or was influenced by someone else. Of course, it is a distinct possibility that whoever wrote it was influenced by God, but it is also a very distinct possibility that were influenced by the world. There's no way of knowing, however. That is why 'rules' should change as society changes.
I do not believe the Bible to be outdated, as it inspires many people to do good. Still, I believe the parts that cause division in society, especially so many years later, should not be relied upon to govern the spiritual lives or the morals of a people who are so different from those who the rules were written for.
/opinion
