Accused of a fallacy? Suspect a fallacy? Ask Dr. Bo and the community!

Quickly register to comment, ask and respond to questions, and get FREE access to our passive online course on cognitive biases!

one moment please...


(also known as: untestability)

Description: Confidently asserting that a theory or hypothesis is true or false even though the theory or hypothesis cannot possibly be contradicted by an observation or the outcome of any physical experiment, usually without strong evidence or good reasons.

Making unfalsifiable claims is a way to leave the realm of rational discourse, since unfalsifiable claims are often faith-based, and not founded on evidence and reason.

Example #1:

I have tiny, invisible unicorns living in my anus.  Unfortunately, these cannot be detected by any kind of scientific equipment.

Explanation: While it may actually be a fact that tiny, invisible, mythological creatures are occupying this person’s opening at the lower end of the alimentary canal, it is a theory that is constructed so it cannot be falsified in any way; therefore, should not be seriously considered without significant evidence.

Example #2:

Priests can literally turn wine into the blood of Jesus.

Explanation: Surely we can examine the liquid and see if it at least changes chemically, can we not?  No.  Because transubstantiation is not about a physical or chemical change, but a change in “substance” -- which, of course, is not a material change and, therefore, impossible to falsify.  Furthermore, the claim is not that it “might be” happening, but it certainly is happening, adding to the fallaciousness of the claim.  The only evidence for this is some ambiguous verses in the Bible -- so ambiguous that over a billion Christians don’t subscribe to the belief that transubstantiation occurs.  So we have unfalsifiability, belief of certainty, and very weak evidence.

Exception: All unfalsifiable claims are not fallacious; they are just unfalsifiable.  As long as proper skepticism is retained and proper evidence is given, it could be a legitimate form of reasoning.

Tip: Never assume you must be right simply because you can’t be proven wrong.


Flanagan, O. J. (1991). The Science of the Mind. MIT Press.

Registered User Comments

Monday, December 30, 2019 - 06:41:06 PM
For an example of another unfalsifiable claim, that isn't inherently ludicrous:

I am a human who is typing on a keyboard.

There is no way that I can adequately prove this, I could be a bot script that posts this same message over and over, I could be a figment of your imagination and should this message be gone the next day you would have no way of knowing if it was left here or not. Proving that you exist to another person is an interesting dilemma.

login to reply
0 replies
0 votes
Reply To Comment

Tom Garcia
Friday, June 16, 2017 - 04:03:34 AM
The cosmological theory named "tired light" turned out false, but not unfalsifiable, as a different alternative falsifiable theory has since been found and confirmed as fact. What was the fallacy in this for those who became convinced it was true?

login to reply
1 reply
0 votes
Reply To Comment

Bo Bennett, PhD
Friday, June 16, 2017 - 07:48:47 AM
Not knowing about that theory, I would have to say that the fallacy is still dependent on the reason why they believed the theory was true.

login to reply
0 votes
Reply To Comment

Become a Logical Fallacy Master. Choose Your Poison.

Logically Fallacious is one of the most comprehensive collections of logical fallacies with all original examples and easy to understand descriptions; perfect for educators, debaters, or anyone who wants to improve his or her reasoning skills.

Get the book, Logically Fallacious by Bo Bennett, PhD by selecting one of the following options:

Not Much of a Reader? No Problem!

Enroll in the Mastering Logical Fallacies Online Course. Over 10 hours of video and interactive learning. Go beyond the book!

Enroll in the Fallacy-A-Day Passive Course. Sit back and learn fallacies the easy way—in just a few minutes per day, via e-mail delivery.

Have a podcast or know someone who does? Putting on a conference? Dr. Bennett is available for interviews and public speaking events. Contact him directly here.

About Archieboy Holdings, LLC. Privacy Policy Other Books Written by Bo
 Website Software Copyright 2019, Archieboy Holdings, LLC.