For example, consider the following argument:
1. Assume that x = 1.
2. Multiply both sides of the equation by 2: 2x = 2.
3. Subtract x from both sides of the equation: 2x - x = 2 - x.
4. Simplify the left side: x = 2 - x.
5. Add x to both sides of the equation: 2x = 2.
6. Divide both sides of the equation by 2: x = 1.
This argument reaches an absurdity because it leads to the conclusion that x is both equal to 1 and equal to 2 - x, which is a contradiction. Therefore, the original assumption that x = 1 must be false.
In general, when an absurdity is reached in a proof, it indicates that there is an error in the reasoning or that the original hypothesis is not true. It can be a useful tool for identifying and correcting errors in logical arguments.