From the series: 6 Ultimate Reasons Not To Be An Atheist?
#2 Atheists cannot believe there is objective moral law
To put the argument another way, humans can recognise the force of gravity because it exists. And even without knowing where gravity comes from, it doesn't change the fact that gravity is there. So it follows that an atheist can recognise an objective morality because an objective morality exists. But the nature of morality is unlike gravity, while gravity is a blind force morality is personal. So it follows that if there is objective morality in nature, then there must be a personal (i.e. interventionist) deity responsible.
So again to subject it to the established criteria, is objective moral law necessary for any particular world-view? And like with meaning, I think the answer is no. Again it's an appeal to consequences. We might desire objective moral law, society might even be contingent on having a moral law, but without objective moral law being necessary it doesn't reflect on the truth of whether there are interventionist deities.
What reach does objective moral law have. Is it contingent on the human species existing? Once it exists, does it have any reach beyond our species? Take killing another for example, does it hold that it is objectively wrong for one man to kill another on the surface of Mars? What about at the centre of our galaxy? Or in the far reaches of the cosmos? I would contend not, that is to say morality is a local phenomenon entirely contingent on our existence.
The obvious does need to be pointed out, humans do indeed have an innate moral capacity, a sense of right and wrong and act on moral impulses. This however doesn't necessitate objective moral law any more than sexual attraction necessitates an objective form of what is attractive. I would say the argument ends here, but I would be remiss if I didn't explore the nature of the question further.
So how can a theist account for morality? The question that any theist needs to answer is what is known as The Euthyphro Dilemma, which goes "is it pious because it is loved by the gods or loved by the gods because it is pious". Or to put it in modern terms, is murder wrong because God says it's wrong or does God say murder is wrong because it is wrong? The first part of the dilemma puts any God-given morality as arbitrary, the latter means that any attempt to reconcile morality through God is begging the question.
The argument in this video comes in the form of an authority, that we can only have morality because of a higher authority (God) gave moral instruct. It seems that those who made the video take the first option, that it is obedience to an amoral entity - lest the argument go ad infinitum or falls into a circular definition.
In the video they fall into what Daniel Dennett calls greedy reductionism by the removal of any possible authority in the material world. After all, it's all just material - blind forces acting indiscriminately. One can't help but think back to Carl Sagan's Cosmos where he laid out the raw materials that make us. The point he's trying to make is that life is more than just the atoms that make it up.
This straw man continues in making an analogy with the chair. That we have no moral obligation not to break the chair as the chair has no personal connection to us. They neglect the obvious, the chair isn't an intelligent agent. The chair itself may not have a moral obligation, but if the chair was owned by a friend they wouldn't take "materialism means no obligation" as a valid excuse.
I'd go so far as to say that theism cannot account for morality, the appeals to authority make no sense for the same reason as it doesn't make it right if a leader of a country proclaims a moral dictum. This sense of objective morality is obedience, it's right for the same reason a parent is right when telling a child what to do. It's an infantile way of looking at what is morality, and given its importance to us as a species it is deserving of something better.
Which brings me to how an atheist can account for morality. I'm not going to argue for objective moral law, rather for how certain moral maxims fall out naturally and how we've come to regard some morals as near universals. And far from morality being an exercise in authority, it's something that comes from the self.
I can already hear the cries of moral subjectivism, yet this could only apply if humans lived in complete isolation. To go back to the chair example. If it were just an individual and the chair, then what is there to stop you from breaking it? Perhaps the consequences of having a broken chair. But if the chair was owned by another, then the relationship between the agent and the chair is changed. Breaking someone else's property could affect your relationship with them.
In there a rule emerges, purely out of the self. Acting in a particular way has consequences, and certain actions can help or hinder others and affect ones relationship to them. It stems from a recognition of one's relationship to the environment around them.
It doesn't end there, game theory can show stable survival strategies fall out of repeated interactions even when weighting is put towards "cheating". In the thought experiment of the prisoner's dilemma, at each interaction it pays to defect. But when the situation is put into repeated interaction, reciprocal altruism emerges as a dominant strategy even though against any one individual it can at best break even.
So what of maxims? While such behaviours like murder and lying are still present, too much of such elements and there is a breakdown of society. The murder rate cannot exceed the birth-rate, too much lying and there's the loss of a vital component of success and fostering relationships. While they are not absolute, they are as close as we can get to objective morality.
There's so much to say on this subject and very little space, so I'll just quickly say this. Evolution can give us a sound base as to why we are moral, but it can't prescribe morality. For such precepts like the golden rule, it can explain why we aspire to it but not why we should aspire to it. It's important to note that we have the capacity to take on ideas, and to think through actions to their perceived consequences. This capacity for knowledge of outcomes gives us the ability to learn from actions in the past and work towards our future.