Here's a quick philosophical sketch of a concept that I think is useful when discussing consequentialist theories of ethics (theories where the moral value of an act is determined by its consequences, like utilitarianism). If I'm missing an important aspect of this, feel free to correct me.
Thomas Nagel's concept of 'moral luck' is exactly what it sounds like: when how moral you are is determined by luck. Intuitively, we think that we can decide (at least in theory) what the right action is before we act, and if stuff happens that's out of our control, then that's not our fault, right? Not according to consequentialists: they argue that if the consequences of your action are bad then your action was bad - regardless of what your intentions were.
Here's a fairly uncontroversial example: two smokers are walking at night, each down a different street in a different city. Both smokers take a last drag and toss their cigarette into someone's front garden - but while the first smoker's cigarette lands in a puddle of water and gets put out, the second smoker's cigarette lands in a spilled puddle of kerosene and sets the whole garden and house alight, killing everyone inside. We would tend to regard the first smoker's act as an asshole move, but nothing too serious, and certainly not criminal. The second smoker, though, is the kind of guy who gets used in cheesy anti-tobacco PSAs. What's the difference between the two? Just luck.
This, says Nagel, presents a problem for consequentialists. How can they provide an intuitive explanation for not considering both smokers equally? There are various ways of dealing with this - expected value consequentialism, drawing a distinction between blame and moral responsibility - but I contend that the problem's larger than Nagel makes out. In my next post I'll explain how.