Although it is often called an optical illusion, this well-known image of a rabbit/duck technically isn’t. Optical illusions are images designed to trick your visual systems into perceiving something that isn’t there, such as motion in a static image. By contrast, the rabbit-duck is an ambiguous image. It plays with your head because it can be interpreted in multiple different and contradictory ways.

Why do I bring this up? Because I think the rabbit-duck, along with other ambiguous images, illustrate one of the reasons why people disagree about politics, due to the fact that multiple high- level narratives can be used to make sense of the same collection of experiences.

Take another ambiguous image:

This image can be interpreted either as the silhouette of a vase, or the silhouette of two faces, depending on which features of image are interpreted as the foreground and which are in the background. The idea of the foreground/background concerns is extremely helpful for understanding political disagreements. Take this excerpt form Scott Alexander:

Some people think of government as another name for the things we do together, like providing food to the hungry, or ensuring that old people have the health care they need. These people know that some politicians are corrupt, and sometimes the money actually goes to whoever’s best at demanding pork, and the regulations sometimes favor whichever giant corporation has the best lobbyists. But this is viewed as a weird disease of the body politic, something that can be abstracted away as noise in the system. And then there are other people who think of government as a giant pork-distribution system, where obviously representatives and bureaucrats, incentivized in every way to support the forces that provide them with campaign funding and personal prestige, will take those incentives. Obviously they’ll use the government to crush their enemies. Sometimes this system also involves the hungry getting food and the elderly getting medical care, as an epiphenomenon of its pork-distribution role, but this isn’t particularly important and can be abstracted away as noise. I think I can go back and forth between these two models when I need to, but it’s a weird switch of perspective, where the parts you view as noise in one model resolve into the essence of the other and vice versa.

The key insight here is that the reason for the disagreement is not really about matters of fact. In this example, anti-government partisans are perfectly able to acknowledge that government does provide some valuable social services, just as the pro-government partisans able to acknowledge that governments are sometimes corrupt. Their disagreement is more about which concerns are central and which are peripheral.

Or you can take another issue, like whether or not we provide asylum to Syrian refuges, and notice that there are very strong opinions on both sides of this debate, despite the fact that everybody involved mostly agrees that 1) a large majority of refugees won’t pose any security risk whatsoever, and 2) Muslims are over represented among perpetrators of mass shootings and other acts of domestic terrorism (jihadists were responsible for about 1/3 of the mass shooting deaths in the past 10 years in the united states, despite the fact that Muslims make up about 1/100th of the US population).

This is certainly not a new observation about political debates, but its illuminates a reason that they can be very frustrating. If you assume that both you and your debate opponent are intelligent enough to avoid buying into any outright falsehoods (a la the fake news), it’s actually quite difficult to articulate a reasons why one set of concerns should be viewed as central, while other concerns should be viewed as peripheral.

It’s so difficult, in fact, that most of the time, partisans don’t even try to acknowledge the ambiguity at all. Instead, they will try to talk loudly about the issues that are broadly consistent with their preferred narrative, and change the subject when issues come up that contradict it. The result is that most political debates feel a lot like acrimonious disagreement over whether it’s a picture of a duck or a rabbit.

This isn’t necessarily to say that political issues are ambiguous, and that all positions are equally valid. For example, on the issue of Syrian refugees, I do actually think that the risk of terrorism is negligible compared to humanitarian benefits. But making a principled argument as to why is very tricky without, misspeaking, being misunderstood, or exposing myself to dirty debating tactics.

There’s a saying that an accusation against a political opponent need not be true in order to be damaging. It simply needs to be harder to refute than it is to sate. If you hear that and think “wow, that’s a really low bar”, you’re absolutely right. This is a large part of the reason why negative rhetoric is so common in politics. It’s easier to say “that policy is a disaster” than it is to explain why a policy X was a good idea.

The affordable care act has problems. It also has benefits. However, if your goal is to defend the affordable care act, it’s a lot easier to talk only about the benefits (and pivot whenever someone brings up problems) than it is to actually assess the problems and make the case that the benefits outweigh them.

This is true about politics in general. Even if your argument is sound, if it’s not simple, it’s not worth making. Negotiating ambiguity isn’t simple, and as a result practically nobody does it.