What is right or wrong have very little to do with what people actually do. The tautology that people want what they want, and that they pursue the things they want, is of little help in deciding whether they ought to get it. Considering related questions my illuminate the issue somewhat.
Why does 5+5=10? This might seem a stupid question to any that can count, obviously 5+5=10, but tell me, what is it about these things that make this so. Whether you are Christian or Islamic, Mayan or Pygmy, if you answer 9 or 15 or any other number but 10 to this question, you would be wrong. There is something fundamentally beyond mere human agreement that makes 5+5=10. In a sense, it is rather like the truth that something is there when you stub your toe in the dark. You can keep kicking whatever it is in your way, it's not going to magically disappear because you want it to. Likewise, you can wish all you want that 5+5=anything else, but that's not going to make it so.
Why does it appear that humans are the only creatures that organize what they do, or at least justify it to themselves and others, based on the very idea of morality? It cannot be because fumbling in the dark for reasons to do x rather than y or z is the most effective way to motivate behavior or benefit the individual or species. Nature designs far more efficient and effective means to do these things in the form of instinct and feeling. People are as often mistaken about the reasons to do something as not, and what they believe to be a true and motivating reason can often turn out to be false. Instincts are honed through long trial and error and are much more perfectly adapted to serve the organism and meet its needs in the environments in which it evolved.
It seems clear to me that morality, seeing as how it is an activity of the mind and reason in its practical application, must follow the general rules of reason-giving. What makes something a good reason? This can only be a reason that others would have no reasonable choice but to accept as well, in similar circumstances. I know all this seems a bit vague and that I'm falling back on the idea that morality is mere human agreement, but there is a deeper and more technical point being made here.
The general method of the categorical imperative, Kant's rule for determining if your proposed action is moral or immoral, follows three steps. 1.) You must state clearly the maxim for what it is for you to do. This involves three elements. (a) You must specify the circumstances in which you intend to act. What is it that makes this state of affairs significantly different from others when it comes to what you intend to do. (b)You must state as precisely as possible what it is you intend to do. (c)Finally, you must state what it is you intend to accomplish through your act, or what your goal is. 2.) You must inquire whether your maxim can be a universal rule. This involves a partly logical test, can your maxim be something that everyone, in principle, could follow. There are a few things this doesn't mean, it doesn't mean that the circumstances you specified in step one actually occur to everybody, that may very well be impossible, and it doesn't mean that everyone or even anyone actually attain the goal specified or would even want to. But if your maxim is something that is impossible for everyone to follow, then it is absolutely immoral. 3.) This third step is the most interesting to me, and one which adds a great deal of subtlety to Kant's system of morality, more than even he was able to fully grasp. As he puts it, this test is whether you can will that your maxim be that universal law. The only interpretation of this that makes sense to me has to do with those goals we talked about in step one. If your maxim were a universal law, would it make more perhaps completely unrelated goals really possible, or fewer goals possible, and not just for yourself, but for everyone. If your maxim as a universal law makes fewer goals really possible, then you shouldn't do it unless there is no other way to attain your original goal. Keep in mind that this step only applies if your maxim is something that everyone could in principle do.
As an interesting exercise, apply this method to the 5+5=10 problem above. Give me some circumstances, I don't care what they are. Let's say you're doing your budget. Give me your goal, perhaps you want to save up for a TV or something. Now, you've come across a situation where you have to add 5 and 5. Could the answer of anything but 10 be something that everyone could in principle give? If they did, wouldn't they make their goal unattainable, or at least not reliably so? Wouldn't it also make the very idea of addition impossible, so that, whatever they were doing, we couldn't say they were adding? Since this seems to be so, giving any answer other than 10 would be absolutely wrong. 5+5=10 is even more special because this is true regardless of the circumstances you find yourself in and regardless of the goals for which you act. Consider something like killing another human being, and you will find that there are some circumstances and some goals which make it permissible, perhaps even mandatory, but others which make it absolutely impermissible. Notice also that this method has nothing to do with what we as humans merely agree to be the case or what we believe is true. Whether a maxim can be a universal law is a matter of rigorous logic and the application of meanings. It has a definite answer that cannot be changed based on mere whim. Whether the maxim as universal law would broaden or impoverish the realm of really impossible ends is a matter of the way the world is really organized, and likewise cannot be changed by mere whim. Notice also that it makes no reference to God and requires no more divinity than is required by the mere existence of the world itself. There is no special divine act required to separate right from wrong.
Please, use your own common sense of right and wrong to test these ideas out. See if you can find something that you would agree is right or allowable that this method prohibits. Apply it to morally problematic situations, such as the permissibility of abortion.
