Business ethics isn't just about what businesses owe customers—it's also about what customers owe in return.Dear Ethics Guy: I enjoy going to the local megabookstore and spending the afternoon there reading the books and magazines they have. The store has big, comfortable chairs, and the clerks never bother me or ask me to leave. Unlike my local library, this place has all the latest publications. I even bring my own lunch to eat if I know I'm going to be there all day. A friend of mine told me that it's unethical of me to do this. I don't think it is, since the store obviously allows the practice (and you can bet I'm not the only one who does it). What do you say? We have dinner riding on it. I say get ready to shell out some cash for the first time in a while, because I agree with your friend. You take without giving, and that's wrong. Just because you have a right to do something doesn't mean it's right to do it. I can't imagine the management of the store looking kindly on what you're doing. After all, they're running a business, not a public charity.The philosopher Immanuel Kant said that a distinguishing feature of right conduct is whether an action can be universalized. Applied here, what he means is that the bookstore couldn't survive if everyone behaved as you do.  Why should you get preferential treatment? Or, as some folks in my hometown of Brooklyn would say, "Who died and made you boss?"It's one thing to peruse reading material before making a purchase. It's another thing to take advantage of the store, whose clerks are too busy helping true customers to have time to shoo you away.If this argument isn't persuasive to you, consider this: If you were the manager of the bookstore, and you knew that someone treated your store as his personal book and magazine collection, wouldn't you be angry—and rightly so?Dear Ethics Guy: I frequent an electronics store that has a liberal policy for returns: If you have the receipt, you can get a full refund for any item you buy, as long as you bring the merchandise back in good shape and within 30 days. Accordingly, I have been able to take home various cameras, video equipment, and even some high-end stereos, and I don't risk losing a nickel.  I basically treat the store as though it were a rental house, without having the burden of actually having to pay for what I use.  You can't accuse me of being unethical, since the store itself allows me to do this. I can't? Well, I will anyway. The reason stores have generous return policies is that they want to create good will with genuine customers. No store could stay in business for very long if everyone acted as you did, and as we saw above, Kant's dictum of treating one's actions as though they could be universalized is a useful way of deciding whether one is acting ethically or not.It's one thing to buy an item in good faith, expecting or hoping to keep it, but discovering that it's not quite what you wanted. It's another thing entirely to take that item home with the intention of using it only for 30 days and then returning it. The difference is between good intentions and purely selfish ones. Certainly you must know that if the store got wind of what you're doing, they wouldn't want you as a customer…and could you blame them?  Of course, strictly speaking, you're not really a customer at all. You're a freeloader posing as a customer.Just as businesses have moral responsibilities to customers, so do customers have duties toward businesses, as you can see from today's discussion.  Originally published on businessweek.com - March 15, 2007Bruce Weinstein, Ph.D. is the corporate consultant, author, and public speaker known as The Ethics Guy. He has appeared on numerous national television shows and is the author of several books on ethics.