Let’s review what you need in your worldview in order to have a rationally grounded system of morality.
You need 5 things:
1) Objective moral values
There needs to be a way to distinguish what is good from what is bad. For example, the moral standard might specify that being kind to children is good, but torturing them for fun is bad. If the standard is purely subjective, then people could believe anything and each person would be justified in doing right in their own eyes. Even a “social contract” is just based on people’s opinions. So we need a standard that applies regardless of what people’s individual and collective opinions are.
2) Objective moral duties
Moral duties (moral obligations) refer to the actions that are obligatory based on the moral values defined in 1). Suppose we spot you 1) as an atheist. Why are you obligated to do the good thing, rather than the bad thing? To whom is this obligation owed? Why is rational for you to limit your actions based upon this obligation when it is against your self-interest? Why let other people’s expectations decide what is good for you, especially if you can avoid the consequences of their disapproval?
3) Moral accountability
Suppose we spot you 1) and 2) as an atheist. What difference does it make to you if you just go ahead and disregard your moral obligations to whomever? Is there any reward or punishment for your choice to do right or do wrong? What’s in it for you?
4) Free will
In order for agents to make free moral choices, they must be able to act or abstain from acting by exercising their free will. If there is no free will, then moral choices are impossible. If there are no moral choices, then no one can be held responsible for anything they do. If there is no moral responsibility, then there can be no praise and blame. But then it becomes impossible to praise any action as good or evil.
5) Ultimate significance
Finally, beyond the concept of reward and punishment in 3), we can also ask the question “what does it matter?”. Suppose you do live a good life and you get a reward: 1000 chocolate sundaes. And when you’ve finished eating them, you die for real and that’s the end. In other words, the reward is satisfying, but not really meaningful, ultimately. It’s hard to see how moral actions can be meaningful, ultimately, unless their consequences last on into the future.
Theism rationally grounds all 5 of these. Atheism cannot ground any of them.
Let’s take a look at #4: free will and see how atheism deals with that.
Atheism and free will?
Here’s prominent atheist Jerry Coyne’s editorial in USA Today to explain why atheists can’t ground free will.
Excerpt:
And that’s what neurobiology is telling us: Our brains are simply meat computers that, like real computers, are programmed by our genes and experiences to convert an array of inputs into a predetermined output. Recent experiments involving brain scans show that when a subject “decides” to push a button on the left or right side of a computer, the choice can be predicted by brain activity at least seven seconds before the subject is consciously aware of having made it. (These studies use crude imaging techniques based on blood flow, and I suspect that future understanding of the brain will allow us to predict many of our decisions far earlier than seven seconds in advance.) “Decisions” made like that aren’t conscious ones. And if our choices are unconscious, with some determined well before the moment we think we’ve made them, then we don’t have free will in any meaningful sense.
If you don’t have free will, then you can’t make moral choices, and you can’t be held morally responsible. No free will means no morality.
Here are some more atheists to explain how atheists view morality.
William Provine says atheists have no free will, no moral accountability and no moral significance:
Let me summarize my views on what modern evolutionary biology tells us loud and clear — and these are basically Darwin’s views. There are no gods, no purposes, and no goal-directed forces of any kind. There is no life after death. When I die, I am absolutely certain that I am going to be dead. That’s the end of me. There is no ultimate foundation for ethics, no ultimate meaning in life, and no free will for humans, either.
Richard Dawkins says atheists have no objective moral standards:
In a universe of blind physical forces and genetic replication, some people are going to get hurt, other people are going to get lucky, and you won’t find any rhyme or reason in it, or any justice. The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil and no good, nothing but blind, pitiless indifference… DNA neither knows nor cares. DNA just is. And we dance to its music. (Richard Dawkins, River Out of Eden: A Darwinian View of Life (1995))
When village atheists talk about how they can be moral without God, it’s important to ask them to justify the minimum requirements for rational morality. Atheists may act inconsistently with their worldview, believing in free will, expecting praise and blame for complying with the arbitrary standards of their peer group, etc. But there is nothing more to morality on atheism that imitating the herd – at least when the herd is around to watch them. And when the herd loses its Judeo-Christian foundation – watch out. That’s when the real atheism comes out – the atheism that we’ve seen before in countries that turned their backs on God, and the moral law. When God disappears from a society, anything is permissible.
WINTERY KNIGHT 
Read the insane history of destruction in the Soviet concentration camp system described in the Gulag Archipelago, penned by Russian writer, Alexander Solzhenitsyn. Solzhenitsyn summed up his thinking in the following way.
“More than half a century ago, while I was still a child, I recall hearing a
number of older people offer the following explanation for the great disasters that had befallen Russia: Men have forgotten God; that’s why all this has happened. Since then I have spent well-nigh fifty years working on the history of our Revolution; in the process I have read hundreds of books, collected hundreds of personal testimonies, and have already contributed eight volumes of my own toward the effort of clearing away the rubble left by that upheaval. But if I were asked today to formulate as concisely as possible the main cause of the ruinous Revolution that swallowed up some sixty millions of our people, I could not put it more accurately than to repeat: Men have forgotten God; that’s why all this has happened.”
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Sorry, that Solzhenitsyn quote was from his acceptance speach for theTempleton Prize in 1983.
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I have published a response to this on my blog.
https://occamsrazorblog.wordpress.com/2017/07/14/response-to-the-claim-that-atheists-cant-justify-believing-in-free-will/
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This response is just a flat denial. The fact of the matter is that if humans are just matter in motion, which is required by atheism, then humans have no free will. Or consciousness, for that matter. Dawkins, Rosenberg, Dennett, Harris, etc. can’t all be wrong.
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A flat denial is an appropriate response to a flat assertion. All you are doing is listing a bunch of atheists who happen to be materialists and determinists. That doesn’t establish a logical connection between the two, as I said, and to counter that I gave examples of atheists who reject determinism.
Anyway, why would it be any more difficult for an atheist to believe in consciousness and free will than it would be for a theist? The evidence for consciousness and free will is introspection, and atheists are just as capable of introspecting as anyone else. You claim that an atheist has to be a materialist, but this is simply not true, and you have given no evidence for it.
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“you have given no evidence for it”. That is because it is self-evident.
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No, it’s self evidently false. It is self evident that someone can consistently both (a) believe that there is no God and (b) believe that the mind is not a physical process.
Now, how are we going to resolve our disagreement, here? We’re both claiming our positions are self evident.
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I don’t think you realize how deluded your view is. If you’re going to profess faith in atheism in the teeth of facts that falsify it like the origin of the universe, the fine-tuning, the origin of life, consciousness, free will, objective moral values and duties, the minimal facts case for the resurrection, the sudden origin of major body plans, etc. then why try to use reason at all? If you’re a lunatic, then just go in for lunacy the whole 9 yards.
Atheism means this: a self-existent universe composed entirely of matter, bound by unbreakable laws. To assert that anything non-physical exists (e.g. – souls that allow free will, objective moral values and duties) requires an explanation for its existence that is IN PRINCIPLE off limits to atheists. That is understood by that atheists I cited, like Dawkins of Oxford University, Provine of Cornell University, Rosenberg of Yale University, Stanford-educated Sam Harris, Daniel Dennett, etc. Although some atheists may want to take a leap of faith and claim realities that only exist in a non-atheist cosmology, we should side with Rosenberg, Harris, Provine, etc. and call this what it is: a leap of blind faith, a belief in fairies without justification (on atheism).
These atheists give you the straight implications of atheism: no free will, no life after death, no objective good, no objective evil, biological determinism, no ultimate meaning, no ultimate purpose, everything dead in the heat death of the universe, etc. These are experts in the field, and they build their worldview off of the foundation of atheism. If you want to assert the existence of things that can only exist in a theistic universe, then you’re just saying “look at me, I’m an atheist who believes in God, but I’m an atheist!”
I mean, I understand that atheism is not a cognitive worldview, and you just invent beliefs ad hoc in order to keep God at a safe epistemic distance, but this is ridiculous.
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I think there is a pattern among atheists. 50 years ago, the universe was eternal – the Secular Humanist Manifesto confidently declared that the universe was eternal. Atheist Carl Sagan taught a generation of students that the oscillating eternal universe was correct, in the public schools, in his “Cosmos” series. Turns out, that model’s been falsified theoretically and experimentally. So, now the atheists just assert that the created universe is somehow compatible with their atheism. Why? Because atheism is UNFALSIFIABLE. It’s a faith that is founded on the need to keep God and his moral demands at a distance. Who gives a rat’s ass what science says? Same thing with free will, consciousness, the fossil record, cosmic fine-tuning, objective morality. Atheism is impervious to facts, because who really cares about facts? This is a worldview driven by sin. It’s sin all the way down, and there’s nothing rational or cognitive about it.
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