What debating tactic does the monk Nagasena use against King Milinda?

Question

_{Source: p 36, Chapter 4, Philosophy ; A Very Short Introduction (2002) by Edward Craig.
Chapter 4 here summarises Milindapañha, the Questions of King Milinda the entirety of which I have not read.}

  The king [Milinda], who is evidently experienced in this kind of discussion (and also has considerable prior knowledge of Buddhism), doesn’t despair but sets out to get to the bottom of it. Realizing that Nagasena wasn’t just speaking of himself, but intended the point he was making (whatever it may have been) to apply equally to everyone, he starts drawing what he takes to be absurd consequences from the monk’s view. If it is true, then nobody ever does anything, right or wrong, nobody ever achieves anything, suffers anything. There is no such thing as a murder, for there is no person who dies. And then a little joke about Nagasena’s status: there was no one who taught him, and no one who ordained him. The tactic is common in debates of all kinds: here are a number of things which we all unhesitatingly take to be true; is Nagasena really saying that they are all false? Or is he going to tell us that his view, if properly understood, doesn’t have that consequence? Nagasena never takes that challenge up directly. By the end of the chapter he has given a hint, from which we can reconstruct what he might have said had he done so. But for the moment the king continues, falling into question-and-answer style reminiscent of many of Plato’s dialogues.

To what debating tactic does the bolded refer? I am inexperienced in debating.

Answer 1

The "tactic" is just the logical rule of reductio ad absurdum. The idea is that you show someone their thesis is false because it generates contradictions. You say p, and I show you if p, then q, so q. However, we have good reason to believe not q. Contradiction. Therefore, not p.