A glass of water handed over to a thirsty man in the desert is a completely different thing than exactly the same glass of water though this time handed over to a man drowning in the sea. This mind game, by itself, would be a field trip for an instrumentalist, as it implies that (a) there is nothing of intrinsic value in a glass of water (the symbol par excellence of flowing and pristine life) and (b) the virtue of the object and the action themselves depend on the consequences produced. Hardcore consequentialism, mind you. Things are not so simple, though. Particularly if one is preoccupied with coherence, for the ultimate conclusions of a stance can lead to very, very scary outcomes.
Welcome to moral philosophy. The delightful mental masturbation peddling concepts such as good, evil, right, wrong, and the like.
[Cliché alert] Let's start from the beginning.
Before handing over glasses of water or going all Iron-Man into conclusions, one has to determine what is good and, to do so, one should isolate the different types of thinking about good. For example, it is not the same to say "x is good" than to say "it is good that he x" and even more different is to claim that "it is good for him to x" or "that's a good x." Let's replace the x now so we can see how different these are: (a) compassion is good; (b) it is good that he gave water to the man; (c) it is good for him to help others; and (d) that is a good glass to pour water in. So, are all these types of good equally good. How about if one of them contradicts the other? Is the first type sufficient to be elucidated? Furthermore, if we focus on the first type of claim, as most moral philosophers do, unless one is a consequentialist and opts for the second type, there is the question of intrinsic value. In our example: is compassion good in itself or, instead, is it good because of what it produced?
Head aching yet? Here comes a drill. The other thing to be aware of is that, if something has intrinsic value, is that something the only one thing which is good (the mother of all goods) or is there a list where we can pile up a whole catalogue of things? But this is a headache for those who are not instrumentalists, because instrumentalists have a rucksack full of things that produce good consequences. The guys with the catalogue are not home free, though, because they have to explain what makes their list the definitive one and, beyond that, how can they be sure that their items in the catalogue can be isolated and not be united by an underlying element which, oh surprise, makes them sole good thing?
So, you get the idea. Good is not a simple thing. And if one has problems defining good then it will get spookier when trying to do moral philosophy. Because, what the hell can one say about the best way to live, or the right action, if one's axiology (the study of value or what is good) is crippled? Yeah, sure, you should live compassionately, giving water to those who are thirsty and not being a douchebag by giving water to those who are drowning, b-but... is compassion good? What type of good is it? Ad infinitum. Well, you get the idea. The painful intellectual poverty of economics is, precisely, that what is valuable (util) is what is consumed, because if it's consumed then it had a price that someone was willing to pay, and that makes utility (value) measurable. Well, sorry, but that's a subhuman way of living.
As one old lady whose husband did something important, or something like that, I can't recall; but the point is that this chick said once that great minds discuss ideas, average minds discuss events, and small minds discuss people. I disagree with the old hag: small minds discuss prices, average minds discuss ideas, and great minds don't discuss at all, they just keep to themselves and avoid talking to idiots. And since I'm not a great mind but merely average (for a dog!) let me tell you how you should start thinking about your own ethical edifice. Because, believe me, dudes, if you don't thoroughly and carefully build your own conception of morality, and spread it responsibly throughout a coherent worldview, you'll be the type of guy discussing people or, worst, prices.
One way of looking at ethics is the Aristotelian way, which basically says that one should take it easy on what is a good or right action, and first focus on what makes you a virtuous dude. So, in our example of the water, it is not precisely bad to be compassionate and give the water to the thirsty dude, but it is cooler to do it because you're a solid chap. That is: yeah, you gave water to someone who was thirsty, but what matters is: were you afraid when going into that desert with a glass of water searching for a thirsty man and conquered your fear? Where you equanimous when that desert sun was toasting your skin and it ached like a bitch? Was that glass of water very valuable to you and, still, you gave it away? Were you honest when giving that glass of water or did you do it just to take a selfie doing it and brag about it with your Instagram followers? Were you affable and cool when giving the water or did you tell the poor, thirsty man that he was lucky that you're so awesome? Did you keep your cool when the man told you that the water was hot and full of sand? And, did you ever get angry that someone had left this poor man abandoned in the desert without water? If not on top of these, you also were clever enough to protect yourself for a desert trip, figured out a way of keeping the water clean and fresh, and were cautious enough to organize a way of getting the hell out of there safe and sound, then, for Aristotle at least, you're the cat's meow.
Was that too heavy? Yeah, well, nobody said Aristotle was your laid-back, easygoing uncle. But don't worry. There's another way of looking at it. That's Kant. And Kant, like all Germans, was as unyielding as an iron pike up the ass. For Kant, it's all about motivations and duty. If one gives water to the thirsty man because one believes that it is one's duty to do so. Since Kant thought that calling pleasure (or any other thing) good without qualifications was pure bollocks, because for example one could take pleasure from watching someone die of thirst, he developed a solid system to know if one was doing something good. Here it goes: if you believe that it should be everybody's duty to give water to those thirsty who are wandering around in the desert and if you did it without expecting that action to lead to something, then Kant loves you.
Then we have the consequentialists. If you ask me, the consequentialists are a bunch of cowards because, trying to appear intellectual, they're just taking the easy road. However, if that's what floats your boat then, by all means, have it with potatoes on the side. There are as many consequentialists as fleas on a street dog, but as we have mentioned before, consequentialists say that an action is moral depending on the result. So, giving water to the thirsty man is the moral thing to do only insofar as the man was spared from dying of thirst. Of course, the easy path is always heavily transited, so there are many types of consequentialists. The utilitarians, for example, think that if giving water to the man gave you pleasure and it gave pleasure to him, then it's all gravy. Others like the egoists, say that if giving water to the thirsty man maximized your good then you're a moral person. And then you have the hippies, which replace "pleasure" or good maximization" with love or knowledge or economic wellbeing, but in reality they're all consequentialists.
Last but not least, there are the pragmatists, but I don't even consider them a legitimate stream within moral philosophy. Because, frankly speaking, those dudes are moral relativists and, to be honest, relativism is what has completely screwed the world up. Here it goes, though, for your sexual pleasure: giving water to a thirsty man in the desert may be moral right here and right now, but maybe not so in other time or place. Which, frankly, is a copout and a bunch of nonsense. Did you know that crawling babies have the foundation to exercise moral thought and action? They do, check it out. And, frankly, should be enough to close all the school departments of sociology, gender studies, English literature, and anywhere else where the mental vomit of postmodernism has nested.
Anyway, rant aside, I want to close this with what is, perhaps, the most important bit of information you can get out of this piece: give water to the thirsty. It's in the Bible. And you should do it even to your enemies. I wouldn't give a glass of water to Derrida, though, and he must be needing it as he is roasting in hell.