(also known as: assuming the conclusion, appeal to common sense [form of])
Description: Asserting a conclusion without evidence or premises, through a statement that makes the conclusion appear certain when, in fact, it is not.
Everybody knows that X is true.
Therefore, X is true.
People everywhere recognize the need to help the starving children of the world.
Explanation: Actually, people everywhere don’t recognize this. This may seem like common sense to those who make the claim, and to many who hear the claim, but there are many people on this earth who do not share that view, and need to be convinced first.
Everyone knows that, without our culture's religion, we all would be like lost sheep.
Explanation: Everyone does not know that. Sometimes, without stepping outside your own social or cultural sphere, it might seem like what you might accept as universal truths are simply truths within your own social or cultural sphere. Don’t assume universal truths.
Exception: Facts that would seem foolish not to assume, can be assumed -- but one should be prepared to support the assumption, no matter how certain one may be.
We all know that, without water, we cannot survive.
Tip: Replace the word “certain” in your life with “extremely probable”.
Variation: The appeal to common sense is asserting that your conclusion or facts are just “common sense”, yet sense is anything but common. We have a tendency to think that many of our beliefs and opinions are “common sense” when, in fact, they are not. We must argue as to why we believe something is common sense, rather than just asserting that it is.