New Zealand philosopher Matt Flannagan wrote a satirical piece on moral duties from a naturalistic perspective: (H/T Michael’s Theology)

Some people claim we have a duty to not rape women, or that religious people have a duty to not engage in wars or acts of terrorism, conduct inquisitions and so on. I think this is nonsense as it assumes there is such a thing as a moral duty and this is false and here’s why:

First, the burden of proof is on he who makes a claim, as an amoralist I am not making a claim I am simply not affirming that moral duties exist, so I don’t have to justify my non-belief in duties. Instead those who believe in duties have to come up with compelling proof they exist.

Second, one cannot empirically verify the claim duties exist so it’s meaningless incoherent nonsense until such verification is given.

Third, no one has yet to provide a proof that duties of any sort exist. Such things if they can be decided at all must be shown to exist by the methods of natural science and to date no one has shown that belief in moral duties is necessary to any scientific theory. Neither physics or chemistry or biology has need of that hypothesis to explain the world.

Fourth, think of all the evil done in the name of duties, almost every war fought through out history has been justified by those who did it claiming they were doing the right thing. Inquisitions, crusades and the suppression of science were all done in the name of doing the right thing and avoiding the wrong thing.

Fifth, if you claim you believe we have duties such as a duty to not rape, I’ll ask you to explain “which duty” do you follow. There are so many different “duties” appealed to. Some people claim there is one fundamental duty, but those who do disagree as to what it is or exactly how to conceive of it. Others claim there are many duties and a small number of people claim there are none. Everyone rejects some concept or account of duty; us ‘adutyists’ just deny one more duty than everyone else.

Sixth – Think of how degrading and contrary to human autonomy the belief in duties is, duties are things we are supposed to live our lives in allegiance to. Rational people can figure out what to do for themselves using reason, we don’t need moral duties to tell us what to do, it stifles human autonomy and is childish to believe in duties.

Seventh – Evolutionary psychology shows us that small children from a very young age have evolved a disposition to believe certain things are right and wrong. The fact we can explain this belief entirely in evolutionary terms shows duties don’t exist.

Eight – What duties you believe is determined largely by your family and cultural background. If you were raised in Iran you would believe you had a duty to execute homosexuals. If you were raised in secular western Europe you would believe you had a duty to support same sex marriage. Clearly therefore, belief in duties is the result of parental and cultural brainwashing and up bringing.

Ninth – We should treat all our beliefs from the perspective of a sceptical outsider, hence we should treat our belief in moral duties from the perspective of moral skeptics.

Tenth – Extraordinary claims require extraordinary evidence. The claim there are moral duties is extraordinary. It claims that there are things that tell us what to do and that we have to do it and this trumps every other reason or desire we have in favour of the action and that failure to do it makes us guilty or blameworthy. No other thing in reality has these features, hence those who believe in duties must provide us with extraordinary evidence.

Eleventh – No-one has ever seen a duty. Duties have no colour, shape or smell, or sound hence they are invisible to sensory perception.

Michael’s blog post on this added two more to the list:

12. Duties were developed by bronze age, desert dwelling peoples and we should grow out of such myths.

13. Those who argue for moral duties use metaethical reasoning and metaethics is not an academic subject.

I think that it’s possible – but not rational – for naturalists to treat moral duties as objective. And that’s good, because otherwise you couldn’t trust them further than you could throw them for even little things. However, I wouldn’t put naturalists into situations of extreme temptation where they felt were not being monitored. I don’t think that they have what it takes in their worldview to do the right thing when no one is watching, especially when it goes against their own self-interest. It’s just not rational for them to care about moral duties, on their worldview – they think that they are just accidents and they think that moral duties are just arbitrary conventions that vary arbitrarily in different places at different times. They are really up front about this view, and I think that we should take them at their word and understand that there are limits to their “moral” behavior. Certainly you don’t want to be in a cloe relationship like a business partnership or a marriage with someone who thinks there is no free will, and therefore no moral duties and no moral responsibility. You might get lucky with them for a while, but eventually, they are going to break down.

For a more detailed look on what a typical non-theist might mean by “morality”, take a look at this post on Uncommon Descent about the famous progressive lawyer Clarence Darrow.

Excerpt:

In 1912, in Los Angeles, for example, Darrow himself went through two trials where he was both the defense lawyer and the defendant – on two counts of attempting to bribe jurors in the union-related murder casein which he had been, as usual, counsel for the defense. In response to the first charge Darrow told the jury:

“I have committed one crime: I have stood for the weak and the poor.”

And at that first trial the verdict was in Darrow’s favour, though it is now generally accepted – even by Darrowphiles – that he was in fact guilty on both counts, plus other similar activities that he was never charged with. At the second trial Darrow proved less able to “soft soap” his way out of trouble, and the proceedings ended with a hung jury. But although Darrow escaped being convicted, he certainly didn’t escape the consequences of his actions.

Firstly he was made to leave California after undertaking never to practice law again in that state.

Secondly he was dropped by the unions as one of their regular attorneys – which is why he spent the last part of his career practising criminal law.

And thirdly, he reportedly suffered what would nowadays be described as a “nervous breakdown” and became, if it were possible, even more pessimistic and morose than had previously been the case.

Clarence Darrow is a hero for atheists like Jerry Coyne, and it’s interesting to see what this Darrow’s “morality” amounted to in practice. When a person denies free will, as Coyne and Darrow do, you can be sure of one thing – nothing evil that they do will be viewed by them as their responsibility. It was the fault of their genes, they’ll say. They will never admit that they are wrong, and their resistance to temptation will be lower than someone who believes in free will – and personal responsibility. I think that at the very core of atheism is this desperate, overarching desire to dispense with moral obligations – or at least to make them optional so that they are only binding if they don’t require any self-sacrifice. That’s why atheists are always celebrating each fresh assault on traditional morality, like gay marriage. They celebrate the breakdown of morality even for things they themselves don’t do, because they just want to be rid of moral duties and accountability entirely. I think there are some exceptions to this, but definitely it’s true of the rank-and-file atheist.