Reductio ad absurdum

Is the form of argument that attempts to establish a claim by showing that the opposite scenario would lead to absurdity or contradiction.

If X is false, then the situation would be absurd. So X is true.

When you want to prove something is true, indicate that if it were false, then the situation would be plainly ridiculous and things might happen that are obviously nonsensical. Make it seem that anyone who believes that the item is false would also be ridiculous and unworthy.

A variant on this is to start by assuming several things might be true, then show that if the (desired) item is true then other items must be false.

Examples:

• If you can't float on water then you would sink like a stone and walk on the bottom of the ocean.
• If people didn't talk to one another, then there would be no society.
• If you were the unhappiest person in the world then you would probably die from sadness. You are still here so you cannot be that unhappy.

'Reductio ad absurdum' means 'reduction to the absurd' and reflects the method of creating an absurd situation rather than there being true absurdness naturally present.

This way of arguing works on the basic principle of offering the other person agreement or stupidity. In effect, it says 'If you do not agree then stupid things would happen and so you are stupid'.

The real fallacy within the argument is that an extreme alternative to agreement is used rather than considering more moderate and realistic alternatives. When arguments are taken to extreme, then most things will appear ridiculous.