Modal Fallacies

What is a Modal Fallacy?

When we talk about what must or what might happen, or what is always true versus what is sometimes true, our words and thoughts have to match up correctly. If they don’t, we could be making a type of mistake called a modal fallacy. The word “modal” comes from philosophy and logic, and it relates to the words like “possible,” “necessary,” “impossible,” or “contingent” we use when we say how things in the world might connect. A modal fallacy is when we get things mixed up about these connections. We can either say that something required will always happen when it’s just one possibility, or we might think something that’s possible just can’t happen, even when it can.

Imagine we’re saying something about a person, like “Sam can run really fast.” Here, “Sam” is the subject and “can run really fast” is the predicate. This fact might be true now, but it might not always be true in every situation. If we slip up and say “Sam must always run fast,” we’re falling into the modal fallacy trap. We’ve turned a possibility into a certainty without good reason. This mistake can lead us to incorrect conclusions and poor decisions because we’re not thinking about the situation in a flexible and accurate way.

Examples of Modal Fallacies

  • The coffee is hot. – The subject is ‘coffee’ and the predicate is ‘hot.’ We agree that coffee can get cold over time. So, we would be mistaken to believe that just because the coffee is hot when we touch it, it will always be hot, no matter what. This example shows a modal fallacy because we turned a fleeting state (hot coffee) into a forever state.
  • Fire burns. – Here, ‘fire’ is the subject and ‘burns’ is what it does. Sure, we expect to be burned by fire, that’s quite a sure thing in everyday life. But, in special cases, such as scientific settings, fire might not cause burns due to safety measures or chemical treatments. Declaring that fire must burn in every single situation is a modal fallacy because we’re ignoring those rare cases where it doesn’t.
  • If Chris and DJ have two dogs and two cats, they must have at least one dog. – This seems to be a clear case: Chris and DJ have animals, so we assume they own a dog. However, the word ‘must’ tricks us into believing it’s an ongoing fact. Maybe they’re only looking after the pets for a day. So, taking a short-term situation and thinking it’s permanent is what makes this a modal fallacy.

These examples highlight the mistake of confusing what’s needed (what has to be) with what’s possible (what could be). It’s easy to wrongly believe something that’s only correct some of the time is right all of the time. And this is what gives the modal fallacy its sneaky nature: making us think something must happen, always works, or is never wrong when, in reality, there are exceptions.

Related Topics

  • Conditional reasoning – This kind of thinking is all about “if-then” scenarios. It can be tricky because we sometimes get confused about what could happen and what must happen. It’s another area where modal fallacies can pop up if we’re not careful.
  • Syllogisms – These are logical puzzles where you have two statements leading to a conclusion. If we use absolutes like “all,” “never,” or “always” in the wrong way, we might create none other than a modal fallacy.
  • Probability – This has to do with odds or how likely something is to happen. Mistakes happen when we claim something will definitely happen when it’s actually just probable.
  • Logic and language – The words we choose impact our logic. The power of language cannot be underestimated, and selecting the precise terms is essential to dodge these modal misunderstandings.


In a nutshell, a modal fallacy is a sneaky logic mistake that happens when we confuse what’s definitely true all the time with things that are only true once in a while. Avoiding this error means keeping in mind that just because something is the case now doesn’t mean it always has to be that way. And just because something sounds like it must be true doesn’t mean there cannot be unusual circumstances where it’s not. It’s about being careful when we link up our ideas and thinking critically about the words we use to describe these links. The next time you hear or make a statement, take a moment to ask yourself: Is this truly an everyday truth, or could it be different under certain conditions? This simple question will help you steer clear of modal fallacies and keep your reasoning on solid ground.