Legal Definitions - reductio ad absurdum

Reductio ad absurdum

Reductio ad absurdum is a Latin phrase meaning "reduction to the absurd." In logic and argumentation, it is a technique used to disprove a statement or argument by demonstrating that if the statement or argument were true, it would lead to a ridiculous, impossible, or contradictory conclusion. By showing the absurd consequences of an opponent's premise, one can effectively argue that the original premise itself must be false.

Here are some examples to illustrate this concept:

• Imagine a city council debating a new ordinance. A council member proposes, "To completely eliminate traffic accidents, we should ban all vehicles from city streets." Another council member might respond with a reductio ad absurdum: "If we ban all vehicles, then ambulances cannot reach emergencies, delivery trucks cannot supply businesses, and residents cannot commute to work or access essential services. This would bring the city to a standstill and cause far more harm than traffic accidents, which is an absurd outcome for a policy intended to improve public safety."

  This example illustrates reductio ad absurdum because the second council member takes the first member's proposal to its logical extreme, revealing that its consequences are impractical and self-defeating, thereby demonstrating the flaw in the original idea of a complete vehicle ban.

• Consider a debate among friends about the best way to save money. One friend suggests, "To save the most money possible, everyone should stop spending any money on anything except basic survival needs like food and shelter." Another friend could use reductio ad absurdum by saying, "If everyone stopped spending money on anything else, then businesses would close, people would lose their jobs, and the economy would collapse. This would ultimately make it harder for anyone to even afford basic survival needs, which is an absurd and counterproductive result for a plan meant to improve financial well-being."

  Here, the second friend highlights the absurd and negative systemic consequences of the proposed extreme saving strategy, showing that the initial premise, while seemingly logical in isolation, leads to an unworkable and undesirable societal outcome.

• In a courtroom, if a lawyer argues that their client could not have been at the crime scene because they were at home, and the prosecution presents undeniable evidence (like security footage) placing the client at the crime scene at the exact same time, the prosecutor might implicitly use reductio ad absurdum. They could state, "If the defense's claim is true, then the defendant must have been in two places at once, which is a physical impossibility. Therefore, the defense's alibi must be false."

  This demonstrates reductio ad absurdum by showing that accepting the defense's premise (the client was home) would require believing in an impossible scenario (being in two places simultaneously), thereby proving the defense's premise to be untrue.