A widely accepted dictum in ethics is that “ought” implies “can”.Philosophers disagree about what exactly this means– but I think thatthe kernel of truth in this idea is that we can’t hold someone morallyresponsible for doing things that he or she couldn’t have not done.One's abilities in some sense set the limit of one's obligations. Presumably, it’sin virtue of their possession of certain abilities that other people lack that some people aredescribed as “very intelligent.” But it’s not clear to me that one ofthese abilities is necessarily the ability to act morally. For myreasons for doubt, go here.
One way to think about oaths would be to regard them as a ritualized form of promise. If so, then one aspect of these questions is: What's the significance of promises? There's a difference between saying that one plans to do something, which can certainly create reasonable expectations and moral obligations secondary to those expectations, and promising to do it, which creates moral obligations that are not secondary to and do not require any such expectations. So one purpose of oaths might be simply to create the sorts of moral duties a promise would. Whether one who makes a promise, or takes an oath, takes those duties seriously is, of course, another matter.
Another aspect of the questions is: Why should promise-making be ritualized as an oath? I can think of two kinds of answers worth exploring. One might be that the public and ritual character of oath-taking might encourage taking it seriously. (Perhaps that used to be true more so than it is now.) Another might be that the ritual form creates legal obligations as well as moral ones. It's one thing to lie and another to lie on the stand, and part of the point of the witness's oath might be (i) to create the difference and (ii) to make that difference vivid.
The injunction “Do no harm” is hard to follow unless one knows whatcounts as harm, and there is no clear consensus about this issue. Itdoes seem that by making a person feel worse, I am harming her. Feelingbad is in itself a bad thing, and it might also lead to other badthings. If I feel bad, then I may not be able to do other things that Iwould otherwise enjoy, things that I might believe have value inthemselves. At the same time, it seems that I could be harmed if I amprevented from learning the truth about my situation. If I have falsebeliefs, I might make choices that I would otherwise not make, choicesthat lead me to feeling worse than I would otherwise have felt. Could Ibe harmed by being led to believe something false about myself even ifthis false belief never leads to any decrease of good feelings or anyincrease in feelings of pain, dissatisfaction, or discontent? Let’simagine that I believe about myself that I am widely admired and deeplyloved by my friends and family and that this belief gives me deepfeelings of contentment and satisfaction. But let’s imagine also that Iam completely deluded: I am ridiculed behind my back and privatelydespised by my friends and family who are hoping to achieve a biginheritance from me. Let’s suppose further that their secret is safe,unless you tell me the truth. Would I be made better off by learningthe truth about myself?
But returning to your particularcase. Even if one has figured out what counts as genuine harm, it'soften a tricky matter in any particular situation to figure out whichcourse of action will cause the least harm. For example, whether agiven patient would be most benefitted were he to learn that his deathis imminent (so that he could make wise decisions about what to do withthe rest of his life), or whether he would be most benefitted by being"blissfully ignorant", will depend on the nature of the person and whatchoices he has. But in any case, most of us value knowing the truthabout our situation, and even if we know that we tend to screw up ourown lives and even if we believe that others could make betterdecisions forus, we still prefer to make informed decisions for ourselves. For allof thesereasons, it has seemed to many that physicians should always discloseto their patients information about their medical condition (including,it would seem, what effect a given drug is having on the patient'shealth).
When you say that you “believe in allowing other people to live outtheir respective journeys in life,” do you make no exceptions? Do youthink that it’s a good idea to let anyone do anything that he or shesees fit? Liberals who are committed to tolerance often draw the lineat actions that threaten great harm to others. After all, even liberalsare committed to laws against murder, fraud, maiming, and the like, andmost don’t worry that their endorsement of such laws reveals a morallyobjectionable intolerance of people who are committed to different lifeplans from their own.
Your question raises interesting questionsabout when and why tolerance is a good thing. I think that many peopleare committed to tolerance because they believe that tolerance is theonly attitude that is respectful of other people. But if a respectfulattitude toward others is what people who are tolerant are attemptingto achieve through their tolerance, then their commitment to tolerancecannot be absolute (i.e., exceptionless). My respect for human beingsmight in some circumstances commit me to being intolerant of otherpeople's actions-- namely, those harmful actions that themselves reveal agrossly disrespectful attitude toward other human beings.
Different general approaches to ethics may provide different answers to this question. Speaking very broadly, there have been three basic approaches to ethical theory. Kant (and others like him, called "deontologists") will argue that the correct way to view ethics is by formulating rules that may be applied universally. In this approach, dishonest will always be bad--though in some cases it might be the lesser of two evils. J. S. Mill (and others like him, called "consequentialists" or more narrowly "utilitarians") will approach ethical questions with a view to what consequences will flow from the act in question (or else from the rules they formulate that will tell us how to act). In this approach, lying can sometimes be good because it will have consequences that have greater utility, all things considered, than telling the truth. Aristotle (and others like him, called virtue theorists) will say that the primary bearer of value is the character of the agent, and not the actions the agent performs. For a virtue theorist, lying would be OK (or even the right thing to do) when and if a virtuous person would lie in that situation. A good example of a discussion on this very point--from a virtue theoretical point of view--can be found in Plato's Republic Book I (331a-c). Plato claims there that it would be wrong to tell the whole truth to someone who was out of his mind (and who might, therefore, react to the truth in an irrational or possibly dangerous way). For a virtue theorist, one-size-fits-all moral principles will always have exceptions, and the sort of case you seem to be worried about may be of this sort. For such exceptional cases, according to virtue theory, good ethical judgment will always be required and can only come from adequate training and habituation.
Atheism and agnosticism are only two reasons not settle moral perplexity by trying to ascertain God's will (see below). Atheists and agnostics will try to find reflectively acceptable principles and rules to guide their actions. It makes sense to start with widely shared rules about nonmaleficence, beneficence, honesty, fidelity, and fair play. Different ethical systems justify and sometimes interpret these rules in different ways. Finding the right moral theory is a matter of finding an ethical system that interprets and justifies these rules in a reflectively acceptable way. In the meantime, most of us will try to regulate our affairs as best we can byapplying these secondary rules.
The interesting question is not so much how is morality possible independently of religion, but how is religion possible independently of morality. Even if we are theists, there's a strong case for thinking that morality is independent of religion. Socrates long ago asked whether something was right because God commanded it or whether God commanded it because it was right (the famous question asked in Plato's dialogue Euthyprho). Socrates reasoned that God's will could not make something valuable, because that would make his preferences arbitrary. Instead, Socrates concluded, the theist should say that God commands what he does, because he himself is good. On this view, God's commands are principled and track what is independently valuable. This also explains why thesists often feel compelled to resolve debates about what God has willed, and how we can ascertain his will, by appeal our moral ideas about what a morally good God could have willed.
But then there should be no deep puzzle about how there could be an objective morality without God, because plausible versions of theism must themselves recognize an objective morality -- that is, one independent of God's will.
You express some thoughts that many people often have (including me).You expressed them in a way that makes no reference to God, but formillennia the natural way of putting one of your questions was to askwhy God — an all knowing, all powerful, all good being — would allowmisery to befall those creatures who abided by His laws. This is thefamous Problem of Evilthat philosophers, theologians, andcountless others have wrestled with forever. (Richard Heck says alittle more about the problem in his response to another question.) Onecan see why theproblem is so pressing for someone who believes in God's existence. Isit pressing, is there even a problem, if one doesn't? For in that case,why should one expect that acting ethically would keep one from harm'sway? Some thinkers have argued that to act ethically is to act in sucha way that, if everyone were to act like you, everyone would findthemselves better off. But even on this view, it isn't the case that toact ethically is to act in a manner that will protect one from misfortune (for others might not act ethically).You hint at another response along these lines: that acting ethically(immorally)is in itself good (bad) for one. (One needn't add that people actethicallyin order to get this good.) If it's true that acting immorally isactually bad for one, a personal misfortune — it brings about, notcancer, but disease of another kind — then perhaps the thought that some badpeople prosper across the board is just an illusion. They might avoid certain illnessesor poverty or earthquakes, but still a misfortune has befallen them invirtue of their immoral actions. Not all misfortune consists in pain,and perhaps the misfortune of having acted immorally is like that.
The expressions "Free Rider" and "Easy Rider" both fit nicely with this cute example. I'm not convinced (yet) that it is not a moral question. When I refrain from making that automotive move--or when I give in to temptation, and do it--I feel my moral sense at work. I'm a cheater, or I rose above the base human urge to cheat. I suspect that utilitarians, deontologists of various stripes, and virtue-ethicists all would have something to say, or pontificate, about it. Jan Narveson, by the way, would say (has said) that the fact that we have such crowded highways is a sign that our lives are getting better (and not, say, environmentally worse).
Update February 14, 2006: I took a passenger van from O'Hare airport in Chicago to a hotel in the Loop last Thursday. The cars on I-90 were crawling up each other's tailpipes. My driver scooted off the interstate at an obscure exit, zipped through the intersection (the light was green), and dove right back in on the other side. When I got out of the van at Club Quarters on W. Adams, I mentioned to him that I thought he didn't save any time by that maneuver. His reply: "Oh? I skipped past 100 cars." Not quite. There were 3 lanes of traffic. On my calculation, he skipped by 33.3333 cars. (Another update, 04/03/06: maybe he skipped by 300 cars!)