Strong Opinions, Weak Proof

Why do people strongly hold opinions they can't defend?

Posted May 06, 2020

Have you ever encountered someone with an incredibly strong opinion who simultaneously lacks the ability to explain why they hold that opinion? Just kidding. Of course you know someone like that.

Although access to the Internet should mean everyone knows why they believe what they believe, people often hold opinions or beliefs without ever questioning them.

But this doesn’t apply to you, right? Well actually, go ahead and ask yourself: When’s the last time you questioned why you brush your teeth?


Since the early 1960s, researchers have been fascinated with a particular type of attitude called a truism. Truisms are opinions or beliefs that most people agree with, yet lack the arguments to support. For example: brushing your teeth.

Although most people strongly believe it is good to brush their teeth, most people don’t have a lot of strong arguments for doing so. Truisms then – like it’s good to recycle or we should strive for equality – are rarely questioned opinions that are nonetheless held with great confidence and extremity.

However, because people rarely have to defend these opinions, when they are challenged, people can be prone to changing their minds. For example, did you know brushing your teeth too much can actually cause irreparable damage to your gums? Or that toothpaste without fluoride doesn’t really make your mouth cleaner?

From those questions alone, do you find yourself a little less positive toward brushing your teeth?

When researchers study truisms, they find that you actually don't even need to challenge their opinions to get them to change them. Simply asking people to list their reasons for holding that opinion – and finding that they didn’t really have any good ones – can be enough to make them less positive toward the topic.

For example, one group of researchers had participants either 1) list as many reasons as they could for why helping people is important, or 2) do an unrelated task. Afterward, participants who were asked to generate reasons in support of this truism actually became less positive toward it compared to those who didn’t list any reasons at all!

Thus, simply forcing a person to articulate the reasons for an opinion or belief of this nature can be enough to get them on the road to changing their mind.

Moral Wrongs

Although the above research highlights how some of people’s strongest opinions are susceptible to simple challenges, there are some opinions that seem impervious to change no matter how logical or convincing that challenge might be.

In one set of studies, researchers presented participants with scenarios where characters committed moral “wrongs” (e.g., incest). Importantly, however, the researchers designed these scenarios such that no bad outcome could possibly occur (e.g., the incest was consensual, protection was used, and the act brought the two closer together).

However, even when participants were unable to provide any articulable reason for why the act was wrong, they still said it was wrong. And likely, you have seen similar effects play out on less “controversial” topics such as in politics today.

For example, no matter how hard you try to convince someone that a politician’s act or a specific bill is not that bad, the other person still perceives it as wrong – even if they cannot explain to you why. In these instances, then, it may be best to avoid trying to undermine their opinions through a rational attack. Instead, try to shift their opinion through other means.

As one possibility, consider how truisms (whether they are in support or opposition to something) are based on the perception that many other people also hold this belief. Thus, if you can show the person that a majority of people do not in fact hold that belief (or at least not that specific version of their belief) you may be able to help shift their viewpoint.

Even still, when it comes to people’s morality – especially as it concerns their beliefs about what is morally wrong – it can be especially difficult to change their attitude. However, if you want to learn more about moral attitudes and what can be done to influence them, read this.


Maio, G. R., & Olson, J. M. (1998). Values as truisms: Evidence and implications. Journal of Personality and Social Psychology, 74(2), 294.

McHugh, C., McGann, M., Igou, E. R., & Kinsella, E. L. (2017). Searching for moral dumbfounding: Identifying measurable indicators of moral dumbfounding.