One reason we might fail to agree (and thus fail to find a common preference) is because there is a conflict of interest. Both people getting what they want is incompatible; it's contradictory. This would be a problem with no good solution.
While conflicts of interest do exist in a very basic sense, there can still be solutions and agreement, at least sometimes. New resources can be created. Preferences can be changed.
To say that agreement is being prevented requires not just for a conflict of interest to exist at all, it requires something more comprehensive. The conflict-of-interest theory says there is no agreement to be found due to this conflict of interest. By implication there is no way to create new resources to get rid of the conflict. And there is no available possibility of people changing their preferences to no longer conflict and still being happy with the new preferences (if you aren't happy with your preference, it isn't *really* your preference).
This conflict-of-interest theory raises some questions. Why can some problems be solved (agreed upon) and not others? Which ones can't be agreed about and how do we identify those? And what really is preventing agreement? We know it isn't just the conflict of interest because that doesn't *always* prevent agreement, so there must be something more that is sometimes, but not always, present. Anyone seriously advocating for this conflict-of-interest theory of the impossibility of always finding agreement should have answers to all these questions.
There are plenty of other theories about what prevents agreement. If we reject the conflict of interest theory that does not force us to conclude there is always agreement to be found.
The conflict-of-interest theory initially seems pretty convincing when you look at examples. I want to eat this bowl of ice cream, and so do you, and we can't both have it. We can both have half, but then we won't get what we want, which is a full bowl. Ice cream is fungible (two bowls of ice cream, same brand, same temperature, same flavor, same size, same toppings, can be exchanged and it doesn't really matter. Like staples or paper clips are fungible you wouldn't care which one you used even if there are microscopic differences.) So in the context of a family trying to get along, ice cream shouldn't really cause trouble. Just go get some more. If you don't want ice cream enough to visit the store, then it's not really too big a deal who gets this bowl. But not all resources are fungible. Sometimes you can't go get more, and then the conflict-of-interest theory has more power. Also, some things are expensive enough that they might as well be unique for the average family. Many families can't afford an extra bathroom, or an extra plasma TV. And there are things with personal significance. You can buy a new dog, but it just isn't the same as the one who's gone on every family trip for five years. You can buy a new doll or blanket, but that might not feel the same either. And sometimes they stop making things and there's only a new version for sale. And many pieces of art are unique. So what if the family has a nice painting and two siblings both want to take it with them when they move out? And the parents might want to keep it as well? Now it seems plausible that maybe there is no agreement to be found without some sort of sacrifice or compromise where people don't really get what they want.
One way to solve these problems is to find something so much better everyone prefers that. Stop worrying about the painting and go to Disneyland. That is something that perhaps everyone will be happy with and honestly prefer. For a few days the painting problem is solved -- no one is being upset by leaving it where it is. And you could follow Disneyland with Hawaii, and then with a European vacation, and so on, and the problem could be solved indefinitely. This is very expensive, but it illustrates a type of possible solution: find some things you care about more and focus on those. It's important to recognize this is a *genuine* solution. They aren't sad, deep down, about not having the painting yet. This is no compromise. They'd really rather have these awesome vacations than have the painting now. So one thing this proves is that changes of preference are possible. Not because you have to, or any pressure, but because once you see this new option you really do want it more. That doesn't mean you can automatically solve the painting problem by offering something someone wants more. You can have $10,000 instead of the painting, OK? Well, I might like that more, but what I'd like *even more* is both! If I only get the money I'll still be wondering why can't I have the painting? I'll miss it. But with the vacations you could offer the person both and they would say: I don't care. I have no use for the painting until I get home, so it really doesn't matter to me. Probably leaving it at my parent's house is best until I get back. So they really do prefer to have the vacation and *not* have the painting (yet). They have found at least temporary, genuine agreement.
All agreements are temporary. People could always change their mind. I'm not saying you can go back on a contract on a whim, or that you will have any right to undo whatever you agreed to. But you might *want* to, and so if what we care about is people continuing to agree and be happy in a family then it does matter even if you have no legal right to change your mind. You might agree your sister can have the painting, and then five years later you decide you miss it and now you want it again. And now more problem solving is needed for both people to be happy with the result. It should be recognized there are good reasons not to change your mind five years later. Your sister has had it this whole time and has gotten used to it; it might be integrated into her life now. Her friends might be used to it. Her decorating scheme might depend on it. She might be far too busy to want to deal with finding a replacement; she might want that part of her life to remain stable. But on the other hand it's entirely possible a new agreement would now be better. Maybe she's tired of it and would easily agree you should have it. Then you'll both change your minds to this new agreement that you have it. And that, too, might only be temporary. Maybe five more years after that you'll give it back to your parents. If your sister said, "No you can't have it now because you agreed," that would not be rational. That isn't a way to find the truth of who should have it. If she wants it that's important. But your old preference that she can have it isn't important anymore because that is no longer your preference. Maybe you should change to have that preference again -- and maybe you will if she describes how much having this painting is making her life better and you think, "wow, I didn't know! I'd never want to take that much away from you!" -- but that will be a new preference based on the present, and you shouldn't be pressured into keeping your past preference. People make mistakes. And it might not have even been a mistake but maybe your situation changed so you want the painting more now.
Agreements being temporary is just like our theories being temporary. We don't promise to keep the same ideas in the future. Even if we think something is true we should hold that idea *tentatively*. People can make mistakes. One thing that means is you can never be completely certain. How could you justify your certainty if you know you might have made a mistake in your arguments or judgment? You can say being wrong is *unlikely* all you want, but if there is ever new evidence that suggests you might be wrong you need to be willing to reconsider.
So one way to find (temporary) agreement is to find an issue that trumps the one you disagree about. Find something more important. And focus on that. Solving the painting dispute with constant luxurious vacations isn't very practical. But this fundamental approach actually does work quite often. It's very good for solving very small problems. If you disagree about a bowl of ice cream then quite possibly that is not worth thinking about, and there are a hundred things you could think about instead that are more important and better. Sometimes couples fight about just exactly who said what, and what should he have said, and what did he mean, and lots of little details. In the scheme of things those aren't very important. They could probably both be a lot happier to drop it and discuss physics, or whatever their interests are. If that was suggested and they considered it, they could very well both prefer it. They might prefer to leave the "who said what" issue in a state of disagreement (they agree about what to do next, but not about the issue itself in some sense. that's the kind of agreement we need for people to go on with life and cooperate). If they both prefer to leave it alone now then they agree about what's important and the problem is solved, at least for now.
What else is there for resolving conflicts of interest? There's making new resources. Not just making them yourself, but finding them works too, or thinking of ways to get them. Anything that adds them to the possible solutions when they weren't there before. Maybe there is a second painting at your grandparent's house that you both like, and once you think of it you can agree to have one each. You might genuinely prefer that. You might think about it and realize your decorating scheme only needs one painting, and that either one will actually fit in really well, so you'll be happy with either one. You might also realize you'd prefer the second painting instead. (You might even both prefer the second painting once it's mentioned, and then start disagreeing about who gets that one. That this could happen proves again that genuine changes in preference are possible. No one is giving anything up in this case by asking for just the second painting. If they secretly, deep down, wanted the first painting, well all they have to do is ask and they'll have it, But they don't want it. They changed their mind.) You might prefer some posters if they were offered to you. They may not be as artistic, but they have cool dragons. Once you realize this is an option and consider it, you might like it better. Or for the ice cream problem you can go buy some more. Lots of problems are very easy to solve this way. They are so easy people don't even count them as problems, or as conflicts of interest. But if you both like a food and there is a limited amount that is a conflict of interest! It's just easy to solve by buying more. That doesn't mean it wasn't a real conflict of interest. What it means is most conflicts of interest are easy to solve. This should be encouraging.
What else is there? You can change your mind about what you want. Not because there is something new and better, or some more important issue, but just because you are persuaded you were looking at things incorrectly. Your sister could explain how important the painting is to her and then you might think it's best she have it. You might explain why you expected to get the painting for years, and your sister might see that was a reasonable expectation and decide she wants you to have it. You might believe the painting is worth a lot of money, but if you were corrected on the facts you might not want it anymore. Because you planned to sell it after a few years. Or because you planned to impress rich friends with it. The point is your plan of how to use it might not work if you learned a new fact. You might consult some home decorators and find out it actually won't fit in with the latest trend you were hoping to use and decide you don't really want it after all. And it isn't just factual theories you could have been mistaken or ignorant about. You could be persuaded of a moral theory. Maybe you want the painting to take it away from your parents, and you could be persuaded that is a bad way to live and you could come to think that you'd be better off not doing that. Another thing that could happen is you could gain some control over your emotions and perhaps learn how to get rid of an emotional attachment to the painting. This doesn't mean giving something up. Maybe the attachment is an inconvenience, and you're better off not wanting the painting (now you can put up those cool dragon posters), but you didn't know how to get rid of the attachment before. Or maybe some emotion is clouding your judgment and a bit of rational discussion can help you see more clearly.
There is also creating new options. New resources are actually useful because they allow new options. You don't have to prefer to get the painting, or not to get the painting. You can now prefer to get the other painting. You can prefer the new option of getting rid of your emotional attachment *and* not having the painting. That's a different option than only not having the painting and its a lot more appealing. Going on vacation and dealing with the painting later is also a new option. New options are where most solutions come from. Lots of them exist from the start by no one has thought of it yet. So just brainstorming some ideas of how else you could deal with the situation might think of something you both prefer and agree to. Why would you prefer it if you don't get the painting or whatever else? Because it has to be better in some way. Maybe you get the second painting and the joy of knowing how happy your sister is with the first one. Maybe you get to feel good about knowing the painting is being put to its best use, and you could not have that if you got the painting yourself.
What if none of this works? You think about it for a while and you don't have a solution you both prefer. Maybe theoretically there is one to be found eventually but you are getting tired of working on this and don't have all decade.
Then we should think about why it isn't working. The conflict-of-interest theory says it doesn't work because there is a conflict of interest. But is that really the problem? So many conflicts of interest were easy to solve. What is setting this apart and making it hard to solve? A special kind of conflict-of-interest theory? Maybe. But what kind? What are its properties? What causes it?
Another reason to fail to find agreement is irrationality. If you both refuse to use reason then of course you are never going to agree. Even if only one person is being irrational that can easily sabotage any agreement. That is a possible explanation that accounts for the continuing disagreement.
Why might we suspect irrationality? Isn't finding agreement hard? Even if conflicts of interest are possible to solve they might still be hard. And there may be other things which also make problems hard to solve, including having only a limited time (before the benefit of a solution isn't worth the effort), or a limited time before it's too late (the bowl of ice cream melts and then no one wants it), or just the difficulty of thinking of good ideas (which really is hard, and when you think of them is unpredictable and might not be soon).
Finding agreement about a philosophical issue, or even a fact, can often be hard. Understanding each other can be hard. Communicating can be hard. Cooperating can be hard. That's all true. But to agree about how to proceed with life does not require that you solve any particular problem, or agree about any particular thing, or learn any particular thing. You can specify all the unsolved problems and even disagreements you want and you can still agree about how to proceed.
You can disagree with your spouse about whether you were right not to tell her something, but still agree about what to do next time a similar situation comes up. That's not strange. It won't be the same situation again. This time you'll know more and you'll have talked about it first. You don't have to ever agree about who was right that one time to agree about what's best to do next time. And you don't need to know the perfectly true morality about telling each other stuff and privacy to agree. You can just share what you each know about the morality of the situation and come to a reasonable conclusion based on the current state of your knowledge. It may be a mistake, but it's the best you know how to do, so you can both agree to it.
There is always a reasonable thing to do given what you know, and even given both of your differing opinions. What should be done if one person thinks X, and one thinks Y, and they have to agree about issue Z? There is an answer to that question. And they can look for it. And they can look at it objectively without worrying about who thinks X and who thinks Y, just take those are premises and consider the whole situation. If they are being rational that shouldn't be any problem at all. There need be no fighting about X or Y no matter how much they disagree. Just establish they don't think they will persuade each other about those issues fast enough to be a good approach, then don't try to. Drop it. And decide what to do despite the disagreement. This can work even for what might appears to be a very major difference. Suppose I'm Christian and you are Jewish and we are discussing what religion to teach our kids. And we try to figure out which of us has the correct religion, but soon we give up on that and decide we'll have to disagree about that. Agreeing about how to proceed is still pretty easy. We can agree to teach our kids about both religions. Or neither. Or we can share with them information about both, and about other religions as well, and atheism, and let them make up their own minds. Or imagine you disagree about which religious holidays to celebrate. Well you might agree to just celebrate all of them from both your religions. And if you try that and find out it's too many holidays and you don't like it, then you might both be happy to pick some not to celebrate since you both see the problem of having too many.
If you are, overall, pretty similar people, then it shouldn't be too hard to come to some sort of agreement that takes into account what you disagree about. There's nothing stopping you. There is always an evenhanded perspective to approach the issue from. If you try that and find you disagree about something else, don't worry, just start over by saying: "imagine we disagree about the first thing, *and* this new second thing, then what would be a good way to approach it?" And you can do that for unlimited disagreements. Every time you get a fresh approach you have a good chance to agree if you are similar people. You'll both be looking at the same scenario and you'll both have (because, by premise, you are pretty similar people) a similar way of looking at it and similar sense of what's fair, so probably you can agree. If you agree most of the time, and you can create an infinite number of different ways to look at this problem and have a chance to agree on each of those, then it usually shouldn't take too many shifts in perspective to find an agreement.
On the other hand, if you are really different people it might not work out so well. It might. Different people often agree about some things. But you might find every time you shift your perspectives to both work on some new thing you look at it wildly differently and find lots of new disagreements and it might be hard even to understand just what the disagreements are. But it's *still* easy to agree! You can agree you shouldn't have kids together, and shouldn't marry, and perhaps shouldn't even be friends. See how extremely easy that was? You can agree you shouldn't put yourselves in any situations where there will be pressure to agree, and you can avoid them, and you can *agree* to take steps to get rid of any such situations you already got into. (By the way, of course, if you do agree about a narrow area, like physics, then it's fine to be in a situation where you need to agree only about physics, like working on the same research project. But do be careful, you will need to agree about slightly more than that like how to write up the results and which journal to publish in.)
But what if you marry someone and find out you hate them later, but already have kids and shared finances? Then you're stuck with a messy divorce! Life sucks. Lots of conflicts of interest about who gets the kids, the house, the dog, etc... Right? Well, that is a good example of irrationality being behind problems and failures to agree on how to proceed, isn't it? Some people divorce amicably. Others divorce hatefully and aren't thinking straight and aren't having rational discussions. And that makes all the difference.
So when it comes down to it, "go your separate ways" is pretty much always an option and if you have so much you disagree about it's best to take that option, you can *agree* to do so. That's the rational thing to do, isn't it? And you can look rationally at how to separate. You might both want that painting, and a list of other items. But you can both consider it this way: suppose two people have a real hard time agreeing about anything, but have to divvy up some stuff, what should they do? And part of the answer, which they can both see, is that they shouldn't expect some detailed discussion of exactly what is best to work well. Neither of them should expect what they consider the perfect outcome to happen. Because they can see the two ideas of the perfect, fair outcome are wildly different, and they both see there is no plausible way to change that, so they can both see the best thing that can happen, the most rational thing, is an outcome that is more simple. They can see there is no good way to satisfy very detailed, delicate preferences they each have, so it's best not to have those at all. And they can see they won't agree about what are good reasons to want items, so they don't need to try to understand each other's preferences very well. They could just auction the stuff off to themselves -- they each get one million points and bid on the items. They can agree to order the items for bidding by alternating picking an item to go next. They can agree to flip a coin to see who picks the first item to bid on. Why shouldn't they agree to that? What can they reasonably prefer? They might reasonably prefer to make lists of which things they most want and negotiate some other way, sure. The auction in particular might not be best. But they can't reasonably prefer to get just what they initially wanted. When they think about it objectively they see there is no good way to make that happen; it's not a rational way to approach the entire situation of two people who disagree to just do what one wants. Even if there is just one item they could just pay money for it. Whoever agrees to pay the other person more money gets it. Or flip a coin. There are plenty of options. There is no reason they can't agree. Unless they are irrational.
The same sort of theory about agreement between different people applies to agreement between different theories (think of it like portions of your personality) within one person. There is a lot of overlap. People's ideas can disagree. A new idea can resolve everything by being better than the others. Something being more important can create temporary agreement about what to do (if your house catches on fire then all sides of the debate about which type of new computer to buy will be happy with the plan of going down the fire escape). There are always shifts in perspective available: if sitting and thinking indefinitely is no good, then you can think: what should a person do who has 20 minutes left to think, then Z event happens, and meanwhile he isn't sure between the ideas X and Y? And there is some rational way to approach that and the answer doesn't have to involve resolving X and Y. And you can think about the answer without invoking the X and Y ideas -- those parts of your brain can be left out. So decide what is best to do and if you are rational then the X and Y theories in your head shouldn't mind being overruled, at least for now, like this. They should be theories that know they might be wrong, and know it's important to live in a truth seeking way and that means sometimes disagreements last a while because you don't know what's true. And if these parts of your personality are at all sane they'll realize you have other things to do so they won't mind being put on hold sometimes. And if you have other very important things they could be on hold for years. And you, your whole personality, can perfectly well agree to that. Unless you are irrational.
* * *
What is an irrationality? It is an area where you are unable to change your views according to criticism or improvements. Where you are stuck with a bad idea or way of thinking that you can't seem to get rid of. So any sort of problem solving, which relies on creating new ideas and finding new options and preferences that people prefer, is sabotaged.
If you have an irrationality or some other part of your personality you don't like then is looking at your past to see where it came from an important part of trying to fix it? No, rethinking events is not a critical part of fixing irrationalities. It is hard to tell what past event caused what facet of your present personality (especially events from your childhood). People are complex! And even if you could figure out the cause that would not automatically lead you to a solution. It could easily be no help at all. Sure now you know who to blame, but knowing who hurt you and how doesn't tell you how to live now, how to construct a fixed person out of yourself.
The idea of "facing" past trauma is also useless. It's true that denial prevents solutions. But acknowledging the problem and finding solutions for it is a different thing than "facing" it which is an unpleasant, scary affair.
Reliving what you think has gone wrong with your life is most often the sign of a victim mentality where you think of yourself as a damaged person, and obsess about your damage and blame people for it. That is not a good way to live. It may be someone else's fault originally, but what you need to do now is improve the life you have, and if you do not that is *your* fault. If you let your past disasters become part of your self-image that is especially bad; they should be kept at a distance because you are trying to get rid of them ("it's not really me! i swear! give me another month and I'll have killed it off").
Looking back is not entirely useless. Sometimes it can give you some ideas, perhaps by thinking about what you could have done differently. But if so it should be fun and interesting, not painful, and there should be no need especially to dwell.
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perhaps belief in spirit is a leap of faith, but for some of us, believing that science and reason have all the answers is a similar leap of faith
This is bad thinking. The entire point of science and reason is they are not leaps of faith: they give reasons which they hope to persuade you with. They do not claim to have all the answers, although they may claim to be capable of finding all answers that are possible to find. But that's only because non-rational, magical thinking cannot find any answers! So reason is what's left, it's the only thing that finds any answers, so of course it finds all possible answers. But you don't even have to believe that. We don't care. The scientific theories we already have are not matters of faith. And we can improve on them. And that makes them a different and better sort of thing that religious faith.
Science is about how to not fool ourselves. Religion is extremely good for fooling ourselves.