These are sometimes major, and these are sometimes minor. But the scale of choices do not always equate with the anxiety these dilemmas stir up within us - which makes us so much more human. And so here I shall treat a relatively minor ethical issue with some logic learned at university all those years ago:
(with apologies to Randy Cohen)
Question:
The convenience store in the lobby of the office tower in which I work has a coupon system in effect. I get a coupon for each coffee I buy, and after I gather seven of these laminated paper tickets in the leather recesses of my wallet, I can turn them in for a free coffee. The coupons do not indicate whether I bought a large coffee ($1.25) or a small coffee ($1.00), and I always buy a small coffee to save the extra quarter - plus a small coffee is sufficient for my appetite. Last week I traded them in to the cashier for a large coffee, who said nor in any discernable way communicated a concern with my actions, and yet I felt guilty for this. Having thought this over, I maintain in retrospect what I did was unethical - was it?
Answer:
Although you were able to obtain a large coffee from the seemingly unwitting cashier, and nowhere was it explicitly stated or written that you must get an equal sized or lesser (i.e. small) coffee, you must subject your actions to moral scrutiny. The agreement also begs the series of questions such as 'if you bought 3 large coffees and 4 small coffees, what size coffee do you get as the free one?'. But these permutations are beside the point, you say you always buy the small coffee, and at the very least did for the series of seven coffees in question. What is at issue is that you deliberately exploited a loophole in the implicit agreement, and your conscience is reminding you of this fact.
Large coffee firms like Starbucks have explicitly written rules and regulations behind a marketing program thusly described. You will also see this carefully structured language on coupons from major food corporations, e.g. that you may get a second item of an equal or lower pre-tax price for an additional X% off, etc... While the small convenience store does supply these descriptions or materials, and the law may allow you to claim a large coffee, the dubious way in which you obtained it forecloses your involvement, and ethics preclude you from claiming the large coffee.
You can not reasonably investigate and learn the explicit and implicit rules of all commercial transactions, but if you suspect you are violating the spirit of an agreement, you should demur. You cannot avoid scrutinizing your understanding of similar implicit and explicit commercial transactions, and extrapolate these to this situation, thusly inferring the rules of this present agreeement. That knowledge compels you to make an ethical choice.