Reductio ad absurdum is used in philosophy to uncover flaws and inconsistencies in various theories and beliefs.
For example, the following reductio ad absurdum argument is inspired by Emmanuel Kant:
“If moral relativism is true and all moral beliefs are equally valid, then the beliefs that ‘helping others is a moral duty’ and ‘helping others is never a moral duty’ must both be valid. This leads to a contradiction, as an action cannot be both a moral duty and not a moral duty simultaneously.”
This argument exposes how moral relativism defies the law of non-contradiction, encouraging further examination and refinement of moral theories.