Reductio Ad Absurdum

By Ashray Sudhir

“The reductio ad absurdum is god’s favourite argument” — George Tyrrell

This is a phrase which is used so often during the bootcamp at Go-Jek Engineering, that it has become one of the strongest tools in my arsenal while arguing about anything. It is also known as “reduce to absurdity”. It is a mode of argumentation in which a proposition is disproven by following its implications logically to an absurd conclusion. The fallacy is in the argument that could be reduced to absurdity and “reductio ad absurdum” is a technique to expose the fallacy.

This form of argumentation has roots in the Socratic method and has been used throughout history in formal mathematics, philosophical reasoning, debating, etc. One of the classic examples is the argument — “The earth cannot be flat, otherwise people would be falling off the edge.”. This shows that it would be absurd to argue that the earth is flat. “Reductio ad absurdum” is only valid when it builds on assertions which are actually present in the argument it is deconstructing, and not when it misrepresents them as a straw man.

The argument takes three principal forms based on whether that consequence is a self-contradiction (ad absurdum), a falsehood (ad falsum or even ad impossible) or an implausibility (ad ridiculum or ad incommodum). In mathematics or logical systems in general, the “reductio ad absurdum” takes the form of “proof by contradiction”.

Such forms of argumentation and reasoning also help in providing a different way of approaching a problem. It helps in rationalizing over a certain problem which helps us converge to certain conclusions about the same which would have taken longer to arrive at.