Why do people disagree? In many cases, it’s due to differences in preferences and values, things that are entirely subjective. However, people also frequently disagree about facts, which should be objective. How does this happen and how can it be resolved? First, we don’t have direct access to physical facts, we only have access to our perceptions of those facts.

Perceptions cannot refute each other, because they are of the same weight. … The fact that perceptions differ has perfectly reasonable explanations: I look from a distance, you look from nearby; I have a cold, you are healthy; I am a human being, another cognizer is a dog; and so on. These facts figure in the explanations of how our perceptions are constituted. … all perceptions, even though they differ, are true. They all have a causal history that physics can explain.

Stanford Encyclopedia of Philosophy, “Ancient Skepticism”

Communication of perception is also imperfect, since it requires translation from mental phenomenon to physical communication medium back to mental phenomenon. Miscommunication and misunderstanding are common causes of disagreement.

Simple misperception and miscommunication aside, people may conflate (perceptions of) facts with inferences or interpretations. For example, suppose you see a mouse in your house. The next day, you find that the box of cereal in your cupboard has a hole in it through which the cereal is spilling out. You may, without even thinking about it, infer that a mouse chewed through the box. While this is most likely correct, the mouse chewing through the box is not a fact you observed, and you could be mistaken. Perhaps your roommate cut a hole in the cereal box to make you think mice were getting into your food so that you would be more motivated to do something about the mouse problem. Stranger things have happened.

We make inferences like this constantly and unconsciously. It is easy to lose track of what you personally perceived versus what obvious inferences you have made. This can be a problem especially when there are emotional reasons for making a certain inference. For example, if you hate mice, you might be more inclined to blame mice for the hole in your cereal box. If you hate your roommate, on the other hand, you might be more inclined to blame them. This is where schemata (or schemas) come in. A schema is a certain understanding of patterns of events that enables us to make rapid inferences. For example, I have a schema about fruit ripeness under which I interpret physical properties of a fruit as indicating the (subjective) concepts “ripe,” “underripe,” and “overripe.” This schema enables me to infer whether or not I will enjoy eating a particular piece of fruit. Since this requires subjective interpretation, I might disagree with someone about the ripeness of a fruit even when we see, smell, and feel the exact same physical object. There is a fact of the matter about how ripe the fruit is (i.e. its sugar content, etc.) but it is not this fact that is the subject of the disagreement. Instead, the disagreement is about how information is inferred and interpreted.

Perhaps by being more aware of interpretations and by making inferences more carefully, disagreements can be avoided or resolved logically. People can and do have irreconcilable differences of opinion concerning interpretation of fact, but these are differences of opinion. In some cases, certain interpretations are more practically successful (“useful”) than others. Some inferences can be verified or falsified. This rest of the problem largely boils down to the psychological problem of emotion and bias getting in the way of truth.