You should also read, "How Can We Be Moved by the Fate of Anna Karenina?" by Colin Radford, and the literature that developed in response to it.
Good luck in your studies! Philosophers have thought quite a bit about self-interest and selfishness. What is often called psychological egoism is the thesis that humans always act in ways that they believe to be in their self-interest (either directly or indirectly), while ethical egoism is the thesis that people ought to do what is (either directly or indirectly) in their self-interest. One point to clarify here is the difference between "selfishness" and "self-interest." If psychological egoism is taken as the view that all persons are selfish because all people act in their self-interest, this seems either false or to involve an odd use of the notion of "self-interest." Clearly many people are interested in living lives of justice, compassion, humility, and so on, but to call such people "selfish" would seem to be quite the opposite of what they are like: namely, they are generous, caring, non-vain, non-pompous, humble. So, I suggest that we use the term "selfish" in ways that pick out traits such as: a selfish person tends to put treat his own needs and desires as more important than others; if food or water is scarce, a selfish person (if he can get away with it) tends to either take or want to take more than his fair share. If a selfish person can achieve an advantage over others through deception, he will be sorely tempted to think of himself first and be tempted to deceive. On this meaning, it does not appear that everyone is selfish (and what might be called psychological selfishness seems wrong) and it also seems that selfishness would do more to endanger social cohesiveness than other traits and motives: like the desire to live in a just society, the motive of caring for others, and so on.
Still, some philosophers have sought to show that rational or enlightened self-interest can lead to benefits. There is a thought experiment called the Prisoner's Dilemma (you can find this outlined on various philosophy website) which is designed to show that while narrow self-interest will lead to the worst overall outcome, enlightened self-interest can lead to the best outcome under the circumstances. And in jurisprudence of philosophy of law, you will find reflection on what penalties or incentives seem required to promote civic life and reduce crime by appealing to the self-interest of citizens. Ideally, you do not want laws that are so lax (imagine the penalty for ponnzi schemes is a few months in jail) that it would be in the self-interest of persons to break the law. Adam Smith is an 18th century philosopher as well as an economist who argued that if persons rationally pursued self-interest they would be guided by what he poetically referred to as "an invisible hand" to bring about the best social benefit.
In terms of books on human nature, I highly recommend two that are accessible, reliable, and clear: Roger Trigg's Ideas of Human Nature and Leslie Stevenson's Thirteen Theories of Human Nature.
A difficult question! There do seem to be clear cases of when jealousy is a vice, especially when it leads to violence and inordinate, misplaced rage. Imagine I am so possessive of my partner that I constantly read his emails to others (secretly and without permission), I rarely trust him and so I regularly interrogate him when he comes back from a trip and I suspect there may have been some dangerous flirting. But as with envy, there seem to be appropriate and inappropriate kinds of jealousy. Imagine I have been a good father to my son, but when he is in college he becomes fixated on an alcoholic, pro-pornography, racist philosophy professor whom my son idolizes and calls "Daddy." Probably my response would not be jealousy, but to seek to expose "Daddy" as a fraud, but I think I might well feel that the affections my son should have for me (or, dropping "should," my son having emotions that are fitting in a father-son relationship) and directing them to a kind of rival, surrogate bad Dad figure. After all I did for my boy, why is he looking to Professor X as a role model and father figure? Jealousy (at least in normal, non-pathological conditions) can also be a way of showing that one cares about a person and a relationship. We are not jealous of things or persons we do not care about. I would only be jealous of a colleague who receives the lion share of adoration on my campus if I cared what students thought and felt about their professors and I felt as though I deserve at least a little bit of affection. A similar point can be made about envy. Envy is destructive if it is in a resentful, grudge mode. This would be a case in which I might envy a philosopher because I want to have her kind of talent and reputation and I want her to somehow fail or loose her edge. But there is a form of envy which may take another form: I might envy a colleague's talents and take great enjoyment in her success and seek to emulate her wonderful example of what it is to be an outstanding generous philosopher who genuinely cares about colleagues and students.
There have been a number of philosophers in the Platonic tradition who have attended to sadness and the whole order of emotions in terms of proper pleasure and pain. You can find the latter in Aristotle, and more explicitly in Augustine's idea that there is an ideal order of love (ordo amoris), proper things we should feel delight or sadness in. In the modern era, one of the more fascinating philosophers to think systematically about values in the Platonic tradition (but he is no commentator on Plato, he is working out a novel ethic) is Max Scheler (1874-1928). You might find his book Formalism in Ethics and the Non-Formal Ethics of Value fascinating.
Great question that gets to the heart of a current debate! If you have a very narrow concept of logic (in which logic only refers to the laws of identity, non-contradiction, and the law of excluded middle) and if your notion of observation is again narrow perhaps only allowing in empirical data then perhaps it is neither logical nor illogical to mourn the death of someone. BUT, you may have a broader concept of observation. For example, in your question you refer to "a loved one." Can one observe the fact that a person is worthy of love or should be loved? I personally think one can. In that case, it would be quite logical (you would be acting with consistency) for you to act in a way that is appropriate when one's beloved one dies. On this expanded front, imagine you truly love Skippy and desire her or his happiness; that is, you believe it would be good for Skippy to be happy and bad if Skippy were to die before fulfilling the desires of his or her heart. Then, surely, it appears you should mourn Skippy's death. Matters may turn out otherwise, however, if you deeply restrict concepts like love, logic, and observation. I suggest the more open approach is the better one in that it captures more fully the way in which our experience is saturated with values that call for our response. You might check out Parfit's extraordinary two volume work On What Matters for a look at the issues and why there is some dispute today among philosophers on the fact/value distinction.
There seem to be forms of hedonistic utilitarianism (maximize pleasure) that might allow for the permissibility of unethical opinions, provided they are not likely to lead to acts of great disutility and the one who has such opinions enjoys holding them. That, in any case, was once advanced as an objection to J.J.C. Smart's brand of utilitarianism. But I suggest it is difficult to insure that unethical opinions don't impact our action. Someone who thinks illegal immigrants should be shot may not do any shooting, but he or she might injure or harm an immigrant, given the chance. Also, ethics (in the west and east) is often (though not always) cast in terms of love and hate one is to love justice, hate cruelty. Someone with the unethical opinions you describe --wanting to shoot illegal immigrants rather than merely prevent them entering one's country seems to be someone who is loving cruelty. And I think many of us do think that cruel desires and pleasures are ethically repulsive in themselves. In the course of some research yesterday, I came across on the web Himmler's speech in the early 1940s about the importance (and duty) of the SS killing all Jews. It is absolutely horrifying. Now imagine a person NEVER acts in any anti-simitic way, but he listens with pleasure over and over again to Himmler and sympathizes with the SS (imagine, in his opinion, never acted on, this person wishes the Nazis has succeeded). I think most of us would see this as a profound flaw or deep sin.
Just one other thought: I have replied without making any appeal to religious ethics (though I suppose the concept of "sin" is in the neighborhood of religion). But for many Jews, Christians, Muslims, Hindus, Buddhists, and others, one's interior life (beliefs and desires) are of profound ethical and religious significance, and not just one's external behavior.
What a wonderful question! You are right about there being a long tradition of sage advise on moderating desire. There is an excellent review of this tradition in the west along with some very insightful observations in the book Emotion and Peace of Mind by Richard Sorabji (Oxford University Press, 2002). He considers philosophical projects of moderating desires and the more radical projects of seeking the complete eradication of passion/desire. Not all philosophers have cautioned us about acting on passion; Pascal, Nietzsche, Kierkegaard and others seem rather immoderate in their advice and lives. But in any case, I suggest that the case for moderation goes hand in glove with the case for the virtue of integrity and freedom. Having sufficient self-mastery and self-understanding to know when one's anger is way out of proportion to the event at hand seems essential for personal integrity. Similarly, one may lose one's ability to think freely and deliberately about one's action if one is consumed with a passionate, but blind lust or jealousy or an unchecked seemingly limitless desire for drink and drugs, and so on. So, I suggest the good of moderation is as important today as in the teaching of the ancient Greco-Roman moral philosophers. In any case, check out Sorabji's fascination book. Good wishes, CT
Fascinating line of reasoning! One thing to question is premise two. Granted if you are angry at someone, it follows that you are judging that the person has done something wrong (wether to you or to someone or something you identify with or value). But it does not follow that you would like to see the person punished or seek to "get back at this person." Imagine you love the person you are angry with and all you really want is an apology or a request for your forgiveness or perhaps you desire a material compensation (the person smashed your car and you want compensation plus replacement of the car). Also, the link between 2 and 4 may need some re-considering. We typically distinguish between revenge and retributive justice. The latter is measured and impersonal: so, in retributive justice when someone wrongfully causes a given harm, there is a proportional penalty (so, assault may call for one year of incarceration and lots of communiity time afterward). But revenge is often personal and without proportion: in a case of revenge, someone who has been midly wronged may actually desire to torture and kill the wrong-doer and his family and maybe even his villiage. So, I suggest that you can wind up with your conclusion that it is good to stay mad only if revenge is good. But revenge seems to not at all be a virtuous or good.
But perhaps two qualifications need to be added: Maybe a commitment to justice requires anger, though not one that seeks revenge. We might think a people are not at all deeply committed to justice unless injustice makes them angry or passionate about the wrongs done. In that sense, maybe we do have a reason to sustain anger. Another time we might see value in sustaining anger is in the case of a victim who has so low a view of her or himself that they are constantly being taken advantage of, even violated in a criminal manner. I am thinking of the abused wife or child who submits to the abuse without resistance. It may be good for that person to sutain anger as part of their sustaining their self-respect and integrity. Perhaps the anger will lead them to report the abuse to police or to otherwise escape the trap they find themselves in.
Great question! You have definitely (in my view) described a disturbing emotional indifference or numbness, but this may not be due to any moral wrong. People might be in such a condition because they have suffered some great trauma or brain injury through no fault of their own. Philosophers have differed in terms of their view of how natural it is for us to empathetic or have sympathy for one another --Aristotle and Locke think we are desposed to care for one another whereas Hobbes almost sees friendship as something we are drawn to for reasons of prudence and self-concern (caring for others is a kind of strategy for us to avoid premature violent death). In natural law theory, lack of concern for the dead or an indifference to personal failure or failing to honor family may be seen as failures to exercise important human virtues (whether or not this is due to a vice or an innocent injury). But some philosophers in ancient Greece taught that we should try to give up desires and attachments --not all Stoics did, but some saw this as an important goal. Even so, the person you are describing may not so much be in the grip of a philosophical theory, as much as they are suffering from a disorder that has an organic or chemical base.
I worry that framing the question this way begs the question -- you seem to assume that any 'choice' comes from or out of 'desire', but isn't that precisely what's at issue? I think we'd need to get a lot clearer on what a 'desire' is before we could answer the question in a satisfactory way ... For example, you seem to consider 'desire' a kind of 'emotion', but philosophers of mind typically would distinguish the two in various ways -- perhaps desires share a kind of 'qualitative character' or 'qualia' with emotions, but desires are typically characterized by having an object or content, one often expressible in words, in a way emotions are typically characterized as 'raw feelings' that may or may not have a specific object or content -- Once you separate desires from emotions, you then need to define desire in such a way as to make it clear that every choice comes from some desire ..... (Charles mentions Spock -- consider this thought. Suppose you could program a computer to do all sorts of complex tasks, including navigating its environment successfully. Maybe it's a robot that's programmed to explore the surface of Mars and send back data. That robot seems to have to make all sorts of 'choices' -- as it navigates its terrain, taking samples of some things, not others -- but do you want to say it has any desires? If not, why must all human choices come from desire?)