The idea that only religious people have any interest in moral
behavior is completely wrong-headed. It's quite easy -- for
someone who bothers to reason it out -- to come to the conclusion that
moral behavior is in your own self interest. In other words, it's
pretty easy to argue that moral behavior optimizes your own world
experience. Read the following carefully, it's simple, but requires
thought.
Here we go:
No man is an island (well, no person is, but why mangle the quote).
There are only a few general sources of pleasure in our lives. We
have the pleasure of our own thoughts, the pleasure of interacting
with our friends and families, and the pleasure we take in
experiencing the material world (skiing, listening to music, playing
a game, watching movies, taking walks in the park - whatever your
thing is). My experience is that my own thoughts are easier to live
with if I've followed the straight and narrow, but perhaps there are
people who enjoy being bad, so we'll assume that, within your mind,
you can enjoy yourself whether you're a good person or not. If you're
an immoral jerk, however, you aren't likely to have a pleasant time
with your friends and family. If you're immoral enough, they
probably won't want to have anything to do with you. Similarly, the
pleasures of the material world are highly dependent on the good
works of others. No one makes soccer balls, you can't play soccer.
No pizza place, no pizza. No grocery store, bummer, you get only the
food you can scrounge on your own. No one feels like making music,
you can't play any CD's. No one invents the air conditioner, you
sweat. In other words, any pleasure you're going to take out of
your interaction with the material world is heavily dependent on the
rest of humanity doing their thing as effectively as possible.
So, big chunks of the pleasure you can experience in life are
dependent on the people around you. If you want to optimize the
pleasure you take out of life in a totally selfish way, your best bet
is to make sure that you aren't a jerk to the people around you and
that you do everything you can to make them as productive as possible;
because the fruits of their productivity are all potential sources of
fun for you. The better the rest of the humans in the world are at
making good music, writing good books, producing good food, thinking
up neat things to do and generally enhancing the world, the better
your life will be. The one thing that you personally can do to make
them more happy and productive is to make sure they're safe from all
forms of attack: from harsh words or financial cheating to adultry or
murder.
This doesn't mean you should give all your belongings to the poor.
You can, of course, and it might do some good, but what really makes
people feel good (at least in my experience) is to be given the chance
to go out and do their own good stuff and find their comfortable niche
in the world. They want to make their own contribution to the big
picture. This means supporting governments and society that promote
freedom and the rule of law.
"Ah", I hear you say, "surely I can cheat a few people. No one will
know if I just steal a little from people who won't miss it or fool
around with just one other person's spouse. I don't have to be moral
all the time." My answer would be, yes, you do; if you really want to
optimize your life. Sure, you might steal a candy bar the next
time you're at the store and no one might notice it. But what if they
do? The minor pleasure that you might get out of that candy bar is
offset by the minor chance that you're either caught (and pay a
penalty) or that you cause someone else to catch hell for not
stopping more shoplifting or that the actions of many people like
yourself put the store out of business. Your small pleasure will
contribute in a small way to events that might cause you to have less
pleasure in the future. Think about those neighborhoods where
shoplifting is so bad that no stores will come there or the ones that
do charge a lot more: no one may have taken a LOT, but collectively
their immoral behavior has made their lives less pleasant.
So, even if your motives are completely selfish (the opposite of the
roots of religious morality), your best move for optimizing your
experience in the world is to live a moral life. QED.