Tarka

Take the case where there are only two rooms, Room A and Room B in a house where X resides and X cannot go out of the house. If X is not in Room B, then he is definitely in Room A. This kind of inference is called “Tarka”.Tarka is called Confutation in English. It is the method of Reductio Ad Absurdum or Indirect Inference. For some philosophers it is Inference itself or an Aid to Inference.

Tarka is defined in section ix (9): False assumption is the deduction of a more extensive thing by the hypothetical assumption of a less extensive one, as in the example: if there were no fire, then there would be no smoke.

Sometimes, a thing may be acceptable largely and attempt to confirm it completely is made by ruling out the contrary. One may not have complete information, however, on the basis of general nature, the absurdity of the contrary is pointed out.It is hypothetical reasoning.

Gautama defined Tarka as a kind of conjectural reasoning(ūha) used for ascertaining the real nature of a thing (tattvajñānārtha), especially when the nature of a thing is generally known (avijñātatattve) but is yet to be fully determined,which reveals the real nature by showing the absurdity of all contrary characters (kāraṇa-upapattitah)http://epgpathshala

This is the same as the short method of indirect proof that we do in formal logic.