Common sense fallacy

by Tim Harding

The American writer H L Mencken once said “There is always a well-known solution to every human problem — neat, plausible, and wrong.” He was referring to ‘common sense’, which can be superficially plausible and sometimes right, but often wrong.

The Common Sense Fallacy (or ‘Appeal to Common Sense’) is superficially similar to the Argument from Popularity and/or  the Argument from Tradition. However, it differs from these fallacies by not necessarily relying on popularity or tradition.

Instead, common sense relies on the vague notion of ‘obviousness’, which means something like ‘what we perceive from personal experience’ or ‘what we should know without having had to learn.’ In other words, common sense is not necessarily supported by evidence or reasoning. As such, beliefs based on common sense are unreliable.  The fallacy lies in giving too much weight to common sense in drawing conclusions, at the expense of evidence and reasoning.

In some ways, scientific methods have been developed to avoid the errors that can result from common sense. For instance, common sense used to tell us that the Earth is flat and that the Sun revolves around the Earth – because that is the way things appear to us without scientific investigation.  Another example of ‘common sense’ is that the world appears to have been designed, so therefore there must have been a designer.

Einstein’s theories of relativity were initially resisted, even by the scientific community, because they defied common sense.  They seemed to belong more in the realm of science fiction than reality, until they were later verified by scientific observations.  Our modern Global Positioning System (GPS) now uses Einstein’s relativity theories.  This initial resistance may have led Einstein to later say that ”Common sense is nothing more than a deposit of prejudices laid down by the mind before you reach eighteen” .

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Filed under Logical fallacies

25 responses to “Common sense fallacy

  1. From ChatGPT: The common sense fallacy is the belief that what is widely believed must be true. It assumes that if something is commonly believed or considered to be “common sense”, it is automatically correct or true. However, this is not always the case, as commonly held beliefs can be influenced by various factors such as cultural biases, personal experiences, and misinformation.


  2. Paul Harrison

    A man and his wife drove past a flock of sheep, and she remarked, “Oh look, Rupert, the sheep have all been shorn”. His reply: “Only on one side, my dear”. Who is correct? Is common sense at work here? Is there a fundamental disconnect between common sense and experience?


    • I’m not saying that common sense is always wrong, just that it is unreliable. Science is more reliable than common sense.


      • Paul Harrison

        Hello Tim, and I completely agree with you. When there is a choice I also go for the science view. A good example could be the supposed miracle of Jesus walking on water. This is explained simply by the mirage effect, but to stone-age people, it was common sense to them.

        Liked by 1 person

  3. Paul Harrison

    Yet, for the vast majority of humankind, it is commonsense which tells us that the Sun rises in the east. Yet, is that true? It is not! Our perceptions, in this case, our sight, appear to tell us that the dearly held belief that the Sun rises in the east is correct, but it in fact means that the earth has once again revolved on its axis. Therefore if we interpret my words with perfect logic we must salute the Flat Earthers, for common sense was all they had to work with.


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  7. The philosopher, Bernard Lonergan, talked about ‘common nonsense’ in this regard, but it’s just as important to be aware of the vested interests and cognitive biases with which scientists distort reality, which makes the above sems oblivious, and so sounds as naive as common sense.

    Liked by 1 person

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  11. Thank-you Tim. Great article. I have heard the whole common sense thing being used against people who just didn’t understand what was happening. I have seen it used as a weapon of oppression as well. “Well person X understands, obviously person Y lacks common sense as they don’t understand what is going on”. Except, unbeknownst to person Y or any onlookers, person X has been slipped some information on the subject that gives them the advantage in knowing things. Not only is information not given to person Y, it is deliberately hidden. This is to prove some point that maybe person Y is just not that intelligent or sharp and deserves how they are being treated.
    This is just stuff I have observed.

    Liked by 2 people

  12. The only people who deride common sense are those who lack it.

    Common sense is impeccable. That is why it is called “common sense”

    Liked by 1 person

    • I can only reply by saying that either you have not read what I have written above or you have not understood it.

      Liked by 1 person

    • Common sense once said the earth was flat, the earth was the center of the universe and the sun revolved around it.

      Liked by 1 person

      • Michael

        No, it didn’t. Common sense said that the sun rises and sets. No common sense would provide revolving, based on simple reasoning. No one, using common sense said that the earth was the center of the universe. There is no assumption of a universe in common sense, at all. Have you ever read Plato?
        Mariners, using common sense, reasoned that the earth was somewhat curved, not flat, by seeing the sails of an oncoming ship before seeing the hull. If you are going to criticise common sense, at least use the scientific process you yourself demand.

        Liked by 1 person

    • Common sense once said since all things fall down, if the earth was round those on the bottom would fall off. However, that was because we did not understand gravity. Thus common sense prejudged without all the evidence. Common sense says heavy things fall faster. A very simple experiment proves it wrong.

      Liked by 2 people

    • Joseph Bodaway

      Invoking common sense indicates you have no argument.


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