That culture can influence moral behavior/ideology is not in dispute. That culture defines morality is. This shows influence, granted, but does not establish that morality is necessarily defined by culture. Anyone can claim the sun is blue. A culture could inexplicably conclude that the sun must be blue despite not appearing blue. The sun is not influenced by what we think about it, even if all our kids start drawing pictures of blue suns.

2. Moral relativism implies the existence of a society in which murder is acceptable.

I’ll grant this - but now you need to establish those factors and show that the probability is indeed so low that the statistical improbability is overcome.

Okay… ( Animal morality? Animals aren’t moral actors…)

This is an individual factor, not a cultural one. I grant sane humans don’t want to be killed - but that would also be true of not wanting to be killed by cars - so why don’t we see streets lined with barriers to keep cars from accidentally running over people? If this is so overwhelming a factor we should see it just as strong in other areas. We do see self-preservation but we don’t see every culture/society regarding personal safety as overriding. To get where you are going, we should see exactly that.

The probability of a particular society having a certain moral belief is dependant on the circumstances of that society. For instance, you may find that a society with a lower ratio of males to females may be more likely to find polygamy socially acceptable.

So, the probability of a society finding malicious killing without caveat be acceptable is going to be dependant on a lot of factors, too. If this probability is rendered incredibly low from factors that every society has in common then we would expect the total lack of societies which find malicious killing without caveat acceptable.

So, let's look at the factors which are common to every society. Every society is made up of humans (we're talking about humans, here, a debate on animal morality or whatever is not something I want to get into really :tongue:) - which is an important factor.

Humans have a lot of things in common. Not wanting to be killed is one of them. For each individual person in a society, not having to face the threat of being murdered every day is an advantage – firstly, it stops them being perpetually fearful for their lives; secondly, it allows them to use the effort they'd otherwise be put into not being killed to do something productive to improve their quality of life and... there are quite a lot of other benefits of not being killed, I would imagine.

Another important factor common to basically all humans (short of the truly sociopathic) is that we do possess (and frequently carry out) alturistic actions. We also have the ability to emphasise with people and to understand how our actions will make other people feel. Being murdered, I would imagine, is not a particularly nice feeling. This isn't exactly perfect, though, as we can (obviously) kill, injure or hate – but still something to keep in mind.

Humans are also social animals. Firstly in the case that we rely on other humans for our survival (see below) and also that we enjoy (and pretty much require) socialising. Both with friends and romantic/sexual partners.

Another feature that societies share is that, in general, they want to stick around. Stability is a inherent goal of any society – this ties in a lot with the “not wanting to be murdered” thing. A stable society benefits everyone in it substantially, as I'm sure you'll agree. A society in which murder was acceptable is not one that's going to stick around for very long.

One other important similarity of the vast majority of societies is the division of labour. The fact that people rely on other members of the society to do jobs (for instance, I rely on the people who purify my water or make my food) is important. You have to trust other people – not only to perform their job well but also to not just run away with your money. The benefits of allowing division of labour to occur are obvious – imagine a society, though, in which murder was considered acceptable – it'd be hard to ensure that that baker you just gave a load of flour to would be around tomorrow for you to pick up your bread and then everyone loses.

While it is true that there have been thousands of societies throughout history, the probability of one emerging (and surviving for more than five minutes) in which murder is acceptable is incredibly low. It is entirely possible – and I would argue probable - that we could see all of the societies that have ever existed finding murder to be morally unacceptable, even when the morality is dependant on the society.

I'd also like to note that societies aren't really ever in a vacuum. The people in them come from other societies (possibly previous ones) and were brought up and taught in various ways. They have neighbours which they might trade with...