"Without God there can be no morality, so why don't atheists go rob people/kill people/[insert crime they currently refrain from here]?!"
This is a crude version of a question I've seen asked around here before. I can't remember his name, but one theist actually believed he could not justify the way he behaves without morality, and that without it he'd steal and commit other crimes. I've always felt this was nonsense, but I could never quite put forth a complete argument as to why. I've thought a lot about it and I'm ready to give it a shot.
I'll use a simple example:
the idea of coming across a stranger carrying a pretty significant sum of money, say 2.5x your monthly income. You're confident in your ability to get the money if you attempt a robbery.
You would quite obviously want the money, but most moral codes dictate that you should not steal and that those who do are bad. Hence, you fail to even remotely consider the option of stealing, and simply repress your desire for (their) money. But what if you didn't subscribe to the idea of morality? Is the logical course of action to pull a knife and force them to hand over their money?
1)
You really wouldn't want to rob someone.
If you admit that you could actually do this, disavow any moral code that would prevent it, and legitimately consider it, most non-psychopathic people would come to realise that they really wouldn't enjoy the experience. I really don't like the idea of pulling a knife on a stranger, scaring them half to death, and taking a large sum of money from them. I wouldn't be thinking "Wow! Think of how many Xbox 360s you can buy with this score!", but instead "Damn, I just robbed that poor person... maybe I'll go and give them their money back."
1.1) You feel bad! See, that's because of morality!
This is the part where people tell me that such negative emotions are the resulting effect of some mysterious godly moral voodoo. That I feel bad because what I did was morally wrong, and I know it. However, it makes sense that humans would evolve to feel bad when hurting others. If humans felt enticed to harm each other, the human race wouldn't have lasted very long. People feel empathy for others and can share their pain, which is where my unpleasant emotions come from.
It is also correct that a person's belief in morality can bring about intense feelings of guilt and shame, but just because you feel something is true, it doesn't mean that it actually is true. Your emotions are not some sixth sense that look out into the world and detect the truth. They're simply a reflection of your own thoughts and beliefs. As a small child your parents ingrained in you the concepts of "should/shouldn't", "good/bad", and "right/wrong". In most cases, parents don't even explain what these concepts are, or how they're in any way meaningful (they aren't imo, but that's a whole different topic). All the kid knows is that their previously loving, fawning parents are now enraged and considerably upset. The reason they give for such a turnaround is that the child behaved in a way they "shouldn't". Just like that, the child now embraces the concept and begins to assign actions to the category of "shouldn't". They assume it's very serious due to the sudden and drastic change in their parent's emotional state, and feel compelled to regain the love of their parents. This explains the source of the negative emotions one feels when they believe they have transgressed their moral code.
2
Life is not a zero sum game, and mutually beneficial relationships are more productive.
Consider your best friend, your relationship over the last ten years, and what the next ten will bring for you both. What is that relationship worth? £2000? £5000? What about a cool £10k? These are rhetorical questions, because most people would say that such a relationship is priceless.
So what if you'd chosen to rob that person at knife point upon meeting them, instead of sitting down and striking up a conversation, enjoying each other's company, and deciding to work together? Working positively with everyone you meet is of great benefit, as you'll surely see if you look at any strong, loving community.
3
Without a trusting agreement to not hurt each other, it is impossible to form relationships.
Let's assume you're a tad psychopathic (no offense), and don't feel empathy when hurting others, nor are you interested in making any friends. It's still in your best interests to agree on principle not to hurt people.
If I said I had no issue with robbing or killing you, you're hardly going to interact with me, are you? This would make it quite hard to live. Therefore, it's beneficial to presently agree to always uphold certain principles, such as refraining from stealing, even if at some point in the future an opportunity to do so would arise.
Of course, you could just lie and pretend that people could trust you not to do these things. However, as soon as you get caught, accused, or even merely suspected, the trust people had will be shattered, and they will be done with you. Your reputation will spread and you will be shunned by your community. Even petty shoplifting could net you a police caution, interfering with certain employment opportunities. Besides, if you're always looking to screw someone over, you'll be worried about the same happening to you, thereby preventing you from any meaningful relationships.
4
The prospect of retribution or punishment.
When discussing morality, people often ask "but what if you knew you wouldn't get caught?". This is highly unrealistic, as you can never guarantee you won't get caught. Even small infractions can lead to a tarnished reputation (and reputation is everything), while much more serious consequences will result from significantly pissing people off.
If caught, armed robbery in this instance would lead to a sentence of 4-7 years, increasing up to 12 years if you hurt them with the knife. You also run the risk of unlawful retribution carried out by the victim's friends or relatives, which could potentially be far worse. What sum of money is worth ruining your life over in this fashion?
So even if you dropped your belief in God tomorrow and your concept of morality went with it, there should be enough reasons here to explain why you wouldn't just start stabbing livers in exchange for iPods. Sure, there are some people with psychopathic tendencies, who are complete loners, who don't think about the long term, and don't care about getting hurt. However, I don't think frowning and telling them how bad they are really makes a difference to these people anyhow.
So the next time someone says "atheists can't believe in morality", instead of trying to explain how they can, maybe I should just respond with: "
so what?"