defeasible

Everyday

(formal, law, logic) Defeasible means able to be cancelled or overturned, for example a right, a contract or a conclusion that may be undone by new facts. tree →

In the lessons

A rare scholarly word. In law, a defeasible right can be taken away if a condition happens. In logic and thinking skills, a defeasible conclusion is a good guess that new evidence could overturn: «Birds fly, so Tweety flies» — unless we learn Tweety is a penguin. It reminds us that many everyday conclusions are «true unless shown otherwise».

Examples

• «Tweety is a bird, so Tweety flies» is a defeasible conclusion. tree →
• The judge said the agreement was defeasible. tree →
• Most everyday reasoning is defeasible: new facts can change our minds. tree →
• The family's right to the land was defeasible if they stopped farming it. tree →
• A scientist's theory is defeasible if a better experiment shows it wrong. tree →
• The rule is defeasible: there are exceptions. tree →

Note

Very formal and rare. Opposite: indefeasible (cannot be taken away). Pronounced «dih-FEE-zuh-bul». Not related to «defeat» in meaning, though the two words share an old root.