"Mere Christianity"

 CS Lewis book, Mere Christianity, can be found here.

This is about book 1 of the book, five chapters across about 20 pages.

Lewis spends a long time saying there are moral laws that exist as abstract concepts in the same way as mathematics. It is debatable, but I tend to agree, so will not address it further. Then, a the end of page 20, we get:

I should expect, for instance, to find that the stone had to obey the law of gravity—that whereas the sender of the letters merely tells me to obey the law of my human nature, He compels the stone to obey the laws of its stony nature. But I should expect to find that there was, so to speak, a sender of letters in both cases, a Power behind the facts, a Director, a Guide.

Thus, his argument is that if the is a law of gravity or a moral law, then there must be a law maker. It is an old argument, but that alone does not make it wrong.

Maths

What he does not say is whether he thinks the laws of mathematics requires a law maker. And to be clear, he does say moral law is like mathematics. And I think he does not say that because for maths it seems far less necessary that you need a law maker.

The internal angles of a triangle add up to 180°C. Did it require God to decide that? Or is that a fact that just is true? As an atheist, I of course say it did not require a law maker, however I am not aware of theists saying otherwise.

But if the abstract laws of mathematics require no law maker, why should moral laws?

Communication

An issue Lewis neglects is how God supposedly communicates these moral laws to us.

If they are built into our DNA, then evolution is able to explain them. Cultures and tribes that cooperate, that value life and reject theft and murder within the social unit, will thrive more than those that do not. If these are traits that can be inherited - which they must be if they are built in - then evolution explains them just fine.

To be clear, they do not need to be inherited via DNA for them to evolve; they could be passed down by word of mouth. I think the actual situation is a combination of the two, and it is interesting to note that chimps display some basic moral behavior.

And there is no sign of God telling anyone. He never told me that murder is wrong. Non-Christians know this as well as Christians. So if God is the law maker, exactly how is he telling us what those laws actually are?

Relative Morality

If God had to devise the moral laws, does that mean they are merely his opinion? God chose for rape and murder to be wrong, but - if Lewis is right - then there is nothing intrinsically wrong with, say, torturing babies.

Amoral God

Furthermore, if something is right because God says it is, then in what sense is God a moral agent? A moral agent can choose between right and wrong - in contrast to, say, a tiger, which kills on instinct. But if God is choosing what is right and wrong, then he surely has no choice to do wrong.

To be perfectly good you have to always do the right thing. but you also have to have the potential to do the wrong thing.

Slavery

A constant bugbear for Christianity is that the Bible states that chattel slavery is okay. How do we fit that with God giving us morality? Does God think slavery is okay? Did he back then, and then he changed his mind?

The point here is that if we got our morality from God - and slavery is wrong - mankind would have known slavery was wrong right from the start. Slavery would likely still have been a thing, but the Bible would would have said it is wrong.

Instead, mankind had to work this out for ourselves.

Lewis on science

As an aside, there are a couple of paragraph in book one that wonderfully illustrate Lewis' understanding of science. 

Page 19:

Every scientific statement in the long run, however complicated it looks, really means something like, "I pointed the telescope to such and such a part of the sky at 2:20 A.M. on January 15th and saw so-and-so," or, "I put some of this stuff in a pot and heated it to such-and-such a temperature and it did so-and-so." Do not think I am saying anything against science: I am only saying what its job is. And the more scientific a man is, the more (I believe) he would agree with me that this is the job of science — and a very useful and necessary job it is too.

Now it must be accepted that Lewis was writing in the 40s, and maybe science education and communication was not what it today, but to think that that is science is woeful.

There is also this, on page 21:

I think we have to assume it is more like a mind than it is like anything else we know — because after all the only other thing we know is matter and you can hardly imagine a bit of matter giving instructions.