There are an incredible range of subjects that people disagree about, but only a small number of core reasons that people disagree. When we encounter complex and difficult to resolve disputes, it can be helpful to break them down in terms of these reasons. This process can help give us insight into what is preventing a consensus from being reached.
Disagreements can be caused by:
1. Facts. People have access to different information. One person has studied physics, another hasn’t. One has spent years reading American news sources, another, Chinese ones. Differing sources will expose people to different facts about the world, which can naturally lead to disagreement. People have had different personal experiences as well, which can lead them to have different world views.
2. Definitions. Words are used differently by different people. One says “God” to mean the god of the old testament, another uses it to mean a guiding force in the universe. One says “art” to mean what is considered valuable by the art establishment, another to refer to creative works that evoke emotion. Typically, people do not even know precisely what they themselves mean when they use words. This isn’t a problem most of the time, but can cause confusion in certain cases. Suppose I take a chair and table, cut them both in half, glue one half of the table to one half of the chair with the cut edges touching, and paint the whole thing gold. Is the object I’ve constructed a table, a chair, both or neither? Our usual usage of the words “chair” and “table” are not well specified in this case, so we have trouble answering the question. I don’t know precisely what you mean by “chair”, and I don’t even know precisely what I mean by it. When I hear the word it triggers associations, memories, an image, but not a precise definition. When people are using different definitions they frequently get into unproductive arguments about those definitions without realizing that they are merely using words differently. “That’s not art, it’s just an old urinal that someone found and put in a gallery.” “Of course it’s art, it’s hanging in a museum, and clearly evokes emotion in the viewer!”
3. Values. People value and care about different things. One person thinks that more life in the universe is inherently a good thing, and so is in favor of increasing the size of the population. Another would prefer less life to be created if that would keep the existing people happier. One man places value on being remembered after he is dead, while another person doesn’t value it because she knows she won’t be able to experience that state of the world. Utilitarians place value on the world containing less suffering, Kantians value a world where certain universal rules are not violated, many people place value on the survival of animals species (even in cases where their survival does not benefit human beings), and so forth. There is nothing strange about different minds producing different labels for what is valuable and what lacks value. It does occasionally happen though that a person’s values are logically inconsistent (for instance, the person claims to value X while disvaluing Y, without realizing that X and Y amount to the same thing). [Comment: Related to values are the issues of tastes, preferences and interests. If you have a taste for chocolate rather than mushrooms, then you have an interest in going to the chocolate store rather than the mushroom store. A disagreement might then ensue regarding which store you “should” go to between you and someone with the opposite preferences. When you say “should” here it may be merely expressing your preference, but the conversation can take the form of a disagreement over what to do.]
4. Signaling. Sometimes people disagree (or claim to disagree) merely to signal information to others. For instance, they might say they disagree with someone they don’t like to demonstrate their dislike, or they might agree with someone they like to make that person like them more. They might say that Shakespeare wrote fantastic plays not because they enjoy reading those plays, but because they want to be respected for being a literary intellectual. They might say that they love the Yankees because that makes them more accepted by their group of friends.
5. Failures of logic. If the people on one or both sides of argument are engaging in logical fallacies or other failures of reasoning, they may end up disagreeing as a result. One person may argue that individual humans will never be able to live for more than 200 years because it has never happened before, while another will claim that we will definitely one day have lifespans longer than 200 years having extrapolated from the increase in longevity over the past 10,000 years. Since both sides have fallacious reasoning in this case, there is no reason to expect them to agree (unless their false logic just happens to lead them in the same direction). We can also include in this category the case where one person doesn’t have sufficient reasoning ability to understand an argument, and so is unable to properly evaluate it. Then, that person may disagree with the conclusion of the argument as a consequence of the argument being inaccessible to them.
6. Competition. Sometimes disagreement is simply about scoring points for our side, at the expense of the other side. In political disagreement, the underlying goal may be to have your own group look good (e.g. to increase support for your group) or to have the other group look bad (e.g. to weaken their power or even humiliate them). For groups within organizations, disagreement may really be about a power struggle: which group should be able to make decisions about which things, and what magnitude of resources should be allocated to each group? We also may just dislike an individual person, and so deny facts that would make them look good, or claim something that makes them look bad. When we are having a disagreement with a person from another group about a standard topic on which our group and their group tend to fight, we should apply some skepticism and wonder whether the disagreement really has to do with the truth at all, or if it’s more accurate to think of it as a battle over group status, esteem or resources.
7. Information processing methods. If people use different methods for processing information, they may end up disagreeing, even if the methods that each person relies on is quite reasonable. Brains do not perfectly update the strength of beliefs when encountering new information. Given limited computational resources, and the constraint that our brains evolved via natural selection, approximations like imperfect updating of credence are to be expected. If two brains both have pretty good but imperfect methods of updating beliefs based on evidence, they may end up disagreeing, even though they are both about as reliable as one another. When we reason explicitly information processing disagreements can also arise. For instance, if we want to estimate the chance that a friend will cancel on us for dinner, it is not obvious how we should weight our knowledge about how often friends cancel on us in general, compared to our knowledge about how often this particular friend has canceled on us. We have more data on all of our friends, which makes that estimate more reliable, but the data on this particular friend is more relevant to the particular case. Ideally, all of the known information should be combined in some way, but one can reasonably disagree about the best way to do this.
8. Default beliefs. If you were to design an intelligent being, it would start off with certain beliefs (implicitly, if not explicitly) and it would be silly, if not impossible, to have it start by assigning a precisely equal probability to every possible state of the world. If the prior/default knowledge of two intelligent beings differs, they may come to different conclusions, even when they processed information in precisely the same way and have access to all the same information. If a human baby, an alien baby, and a robot were raised in precisely the same environment, they might end up believing substantively different things about the world merely because their brains have different built in assumptions. Their brains might, for instance, start out assuming different things about the nature of other intelligent beings.
9. Self-interest. On a basic level, Bob probably cares about Bob’s well being more than he cares about Karen’s, and Karen probably cares about Karen’s well being more than she cares about Bob’s. While Bob and Karen may explain a disagreement in other, less self interested terms (e.g. “I think it’s best for the company if we move offices”), it could simply be that they are each acting self interestedly and have different interests. More subtly though, it often happens that people’s brains will make it hard for them to see the truth, because the truth will have negative consequences for them. Take, for instance, the case of someone raised their entire life in an extreme cult. If they encounter evidence that the cult’s beliefs are false, they are likely to experience intense anxiety, because finding out and believing that the cult is wrong could have very severe negative consequences for them, such as causing them to be cut off from all of the people they love. Hence, there may be intense psychological pressure not to think about this evidence anymore, or to come up with a rationalization for why the evidence must be wrong, which will be immediately rewarding by eliminating the anxiety. Effectively, your brain may not let you see the truth because it anticipates the negative consequences from doing so, and it is trying to protect you from those consequences.
Suppose that two intelligences (people, aliens, A.I.s, etc.) exchange information about their beliefs, and their reasons for having those beliefs. If they start with the same default beliefs, employ the same information processing methods, do not make errors when they explicitly reason, are able to follow each other’s reasoning, share the same values, use the same definitions, and have access to the same facts (for instance due to exchanging factual information with each other), then you should expect those two intelligence to reach agreement.
Note, however, that these nine categories of disagreement are not entirely independent from each other. For instance, the distinction between bad information processing methods and illogical argumentation can blur. A poor choice of definitions can also be a form of illogical thinking when those definitions are meaningless (“Let’s define a squircle to be a square circle”). And the distinction between default beliefs and built in information processing methods can be fuzzy as well, since the effectiveness of information processing methods may depend on assumptions those methods make about the environment. It is also a possibility that there are disagreements which arise that aren’t due to any of the nine reasons listed above (should any other types of disagreements occur to you, please post them in the comments below!).
Let’s see how this categorization system can help us understand real world debates. As our example we’ll use the debate about when abortion should be legal (a convenient choice because this debate has many facets and great complexity), taking into account the arguments frequently used by liberals and conservatives in the United States. A 2006 survey found that 60% of self-described “liberal democrats” thought that “abortion should be generally available”, versus 17% of self-described “conservative republicans”. Furthermore, 68% of these conservative republicans thought it should be either “illegal with few exceptions” or “never permitted” versus 23% of the liberal democrats. We’ll stick to considering this debate in terms of the first six reasons listed above that cause people disagree, since these six are often very useful frames of analysis.
1. Facts. Liberals and conservatives tend to be exposed to different information. For instance, it would not be surprising if liberals were more likely to hear about ways in which women are negatively impacted by not having access to abortions, while Conservatives were more likely to hear about women who regret having had abortions. Most of us tend to spend time with people that share many of our beliefs, and to read news from sources that are at least somewhat aligned with those beliefs. That means that the facts and ideas we hear tend to support what we already think is true. We should expect the friends and news sources of liberals to propagate more information supporting liberal values, and likewise for the friends and news sources of conservatives. Even google reinforces this tendency, when we happen to structure our queries in such a way that the results confirm our beliefs, and when Google automatically customizes our search results to be drawn from sources that are similar to those that we visit frequently.
The obvious solution to disagreements over facts is to exchange information with those you disagree with. This works well when people on the other side of the debate trust your sources as much as you do, and when they are willing to allow facts to change their minds. In practice, both of these assumptions are frequently violated. People commonly disregard information that contradicts their own beliefs, and latch onto the information that supports what they already think. When you encounter someone doing this, you can try asking the other person “what information WOULD make you change your mind about this issue, if that information were actually true?” That at least has a chance of getting the person to pre-commit to changing his or her mind if the relevant information can be found.
2. Definitions. The abortion debate is frequently phrased in terms of whether a fetus can be said to be a “person” (or, similarly, a “human being”), with the argument going “It is wrong to kill a person, so if a fetus is a person, killing it is wrong.” This would seem to imply that if we can just decide whether a fetus is a person then the question will be answered. But this begs the question of what we mean by “person.” We all agree with that Barack Obama is a person, but the usual definition we use for person isn’t clear cut enough to decide whether that word applies to the fetus case. And even if it were clear cut, it wouldn’t matter. The underlying question is not whether a fetus is a person, but whether we place disvalue on the death of fetuses, and if so, how much, and why. Phrasing the question in terms of whether a fetus has the status of person is bound to lead to disagreement, since intuitions about what “person” means differ quite substantially, and when one person says “a fetus is a person” and another says “a fetus is not a person” they may well not being using the word person to mean the same thing.
A handy trick for helping to resolve disputes over definitions is to taboo your words. Basically, this means replacing any confusing or fuzzy words with other words that get more closely at what you are trying to say. So, rather than “person” say “being that can suffer”, or “creature that cares about whether it lives or dies”, or “thing that is or one day will be an adult human”, or whatever else it is that you are really trying to denote with that word. In other words, if you’re stuck debating whether something is or is not a person, ban the word “person” from the conversation and use a more descriptive phrase. Now see if that allows the conversation to move forward.
3. Values. Some people place negative value on suffering, and believe that aborting a fetus is wrong if it causes the fetus to suffer, and that it is not wrong if there is no suffering. Others place negative value on the death of conscious entities, and so oppose abortion at the point that a fetus can reasonably be said to be conscious. Still others oppose depriving a being of its potential for future experiences, and so are anti-abortion on these grounds. Some people value rights, and believe the mother’s right to look out for her own interests trump those of the fetus until the point when the baby is self aware enough to get rights of its own. Still others value the life of anything that will become a human being, which includes fetuses.
Even though people can value different things without either of them being wrong, it still is sometimes possible to change what people are willing to say they value. For instance, you can try to demonstrate to them that one of their values conflicts with another of their values, which can cause one of those values to shift. Or you can try to show them that they do in fact value something that they claim not to, and prove it by means of an extreme example designed to provoke emotion.
4. Signaling. Abortion debates sometimes devolve into claims that those in favor of abortions are “against life” or that those opposed are necessarily “against women”. Obviously those who are pro abortion almost never actually want fetuses to die, they just want the mother to have a choice of whether to give birth. Likewise, there are of course reasons one may oppose abortion due to concerns about the loss of life of the fetus while simultaneously supporting rights for women more generally. When we use phrases like “against life” or “against women” they typically serve to demonstrate our group identity, and label the other side as bad guys. They say a lot about our emotional reactions and how we want our side and the other side to be viewed, but little about what the other side actually believes.
5. Failures of logic. Bad arguments are a prominent part of the abortion debates. Some such arguments fail because they rely on the ambiguity of words and assumptions that are left unexplained. For instance: “fetuses are human life, and human life is sacred, so killing fetuses is wrong.” Some take logical leaps that are not sufficiently filled in: “since an early term fetus can’t survive without the mother’s body, it is the mother’s choice whether to kill it”. Other arguments are true, but don’t demonstrate the claim they are used to support: “abortion is dangerous to mothers because it caries health risks”. Of course, this leaves out the fact that child birth itself carries substantial risks to the mother. Other arguments lead to question begging: “A women has a right to control what happens to her body, so she is justified in having abortions.” Where does this right come from, and if there is such a right, why does it trump other rights that might come into play in this case?
Convincing other people that their arguments are illogical, and identifying failed logic in our own arguments can be quite hard. A helpful tactic for dealing with illogic in others is to ask them to clarify their argument, rather than outright attacking it. For instance, saying “could you explain why X implies Y, as I’m having trouble seeing the connection” rather than saying “X doesn’t imply Y, you idiot.” Generally, the more people feel attacked, the more they feel they need to defend themselves, and the more likely it is that discussions with them will devolve into fights. Another useful technique, if you’re having trouble making headway, is to rephrase your disagreement with them. If they claim “X or Y” must be true, rather than just saying “that isn’t right” for the third time, you can try “Can you think of any other possibilities besides X and Y? Because I’m not convinced that one of them has to be true.” Or if someone says “X implies Y” and you’re quite sure it doesn’t, you can ask “so if Y were not true, you think that would imply that X is not true?” This helps people look at their own claims from a different angle, which may make them realize problems in their arguments that they didn’t identify before.
6. Group Competition. At first glance the argument may be about abortion legalization, but is it really about abortion legalization? Or is it more about trying to show that the other group is bad, for instance by trying to demonstrate they have no respect for women’s rights, or that they have no respect for the rights of the unborn? It may be that this is better understood as a fight about whose group is good or bad, or an attempt to increase group membership (if the disagreement is carried out in the public sphere), rather than a debate over what’s true.
When we encounter a complex and difficult to resolve disagreement, we can gain insight into why it is occurring and how it might be resolved by considering the roles of the nine (and particularly, the first six) fundamental reasons for disagreement: (1) facts, (2) definitions, (3) values, (4) signaling, (5) failures of logic, (6) group competition, (7) information processing methods, (8) default beliefs, and (9) self-interest.
Robin Hanson explained disagreement in terms of the well-known construal-level theory in this post: http://www.overcomingbias.com/2009/01/disagreement-is-nearfar-bias.html
I find it difficult to accept that humans have sufficiently divergent values as to actually invoke huge amounts of disagreement. Rather than people actually valuing different things, what people value usually only appears on the margins: most of us agree that things like music and laughter are good, but we fiercely disagree (for reasons other than values!) about what kind of music is good, or what is funny. (Which is sad. Whatever makes you laugh is funny, and you don’t score extra points for enjoying a certain type of humor.) Number four on your list of seven causes ought be downplayed, I think. More likely, where a values differential appears, it’s the result of either insufficient or incorrect factual beliefs, or plain-old miscommunication.
Also, the link under “logical fallacies” is broken.
When I said “number four” in that comment, I actually meant “number three”. Please adjust it accordingly in your imagination.
Thanks. Added a note in the post about tastes. Also, fixed the broken link!
Hmmm. 2011. That was a year.
Glad to see someone else is interested in why people disagree. Sad to see my primary interest in the question not tackled. Very vague, faint light in a fog I’m looking for here, but it’s less like “here are the multiple causes” and more like a root similarity leading to a conclusion about how life might ought to be, less like how life ought to be dealt with, more like how to enjoy it, stripped down and tailored to fit everyone including me, and you know I generally reach the conclusion that such a thing is unlikely to exist (with enough concreteness to still be palatable three minutes later) and that is why I so frequently erase all that I have written.
Good article. Surprised to see no mention of Aumann’s agreement theory though.
individual differences are also worth considering. for example, I am a programmer, its good for me if, for example, the government adopts the law that is good for programmers.
and another person may be a lawyer, and he may be inclined towards government adopting law that helps layers(ironically) somehow.
so they might agree about everything, have the same beliefs and values and respect the same stuff, but they will definitely disagree about who to vote in elections.
so this type of disagreement may happen with perfectly reasonable people that dont make any mistakes in above stated 8 categories.
it may not be the case of agreeing to disagree but resolving might still not be possible. sometimes resolution also depends on how complicated the topic is, and you cant resolve all disagreements.
Good points! This would go under the 8th category “Self-interest”, but I don’t do a good job of making that clear. I’m going to update the post to make it clearer. Thanks!
Yes, totally! The category “Self-interest” is exactly the name for it. Just the example was about something else and that was a bit confusing for me I guess. I am interested in your ideas about resolution also. It is a really Great article!
These different reasons (or causes) for disagreement share a lot of things in common. By clear thinking we should be able, using analytic logical techniques, to reach a fewer number of more basic reasons that the 9 kinds presented here. In other words, what is claimed to the result of clear thinking is actually only a half-way stage in reaching this desirable target.
I love this. Do you know any blogs or whatnot devoted to analyzing contentious issues similarly to what you did for abortion, but in greater depth? I could write and read that kind of thing all day.