Argumentum ad absurdum

On the moral obligation to stop shit-stirring:

"Utilitarianism – the idea that we should evaluate the moral worth of an action by its consequences, and that the best actions are those that bring about the most good for the most people – is the ideal public morality for our troubled age. It requires us to focus not only on what we do, but also on what we didn’t do but might have done. Non-action in the face of threats such as climate change, pandemics and technologically facilitated extremism has moral implications of its own, and it’s utilitarianism that offers the most emphatic responses to these problems."

...

"There are far too many people who reflect that, since they aren’t deliberately harming the environment and aren’t personally racist, they are therefore absolved from acting. There’s a problem when it seems reasonable to respond to a utilitarian’s demand that one think about what one could do by saying: ‘I think I understand your utilitarian argument for a moral obligation to immediately address climate change, but isn’t utilitarianism the theory that says it’s fine to kill babies? Why should I listen to that?’" [shooting the messenger fallacy = a metaphoric phrase used to describe the act of blaming the bearer, in this case an argument, of unwelcome news]

In logic, reductio ad absurdum ('"reduction to absurdity"'), also known as argumentum ad absurdum ("argument to absurdity"), apagogical arguments, negation introduction or the appeal to extremes, is the form of argument that attempts to establish a claim by showing that the opposite scenario would lead to absurdity or contradiction. It can be used [in an attempt, as above] to disprove a statement by showing that it would inevitably lead to a ridiculous, absurd, or impractical conclusion, or to prove a statement by showing that if it were false, then the result would be absurd or impossible. Traced back to classical Greek philosophy in Aristotle's Prior Analytics (ἡ εἰς τὸ ἀδύνατον ἀπόδειξις, lit. "demonstration to the impossible", 62b), this technique has been used throughout history in both formal mathematical and philosophical reasoning, as well as in debate.

Reductio ad absurdum was used throughout Greek philosophy. The earliest example of a reductio argument can be found in a satirical poem attributed to Xenophanes of Colophon (c. 570 – c. 475 BCE). Criticizing Homer's attribution of human faults to the gods, Xenophanes states that humans also believe that the gods' bodies have human form. But if horses and oxen could draw, they would draw the gods with horse and ox bodies. The gods cannot have both forms, so this is a contradiction. Therefore, the attribution of other human characteristics to the gods, such as human faults, is also false.

Greek mathematicians proved fundamental propositions utilizing reductio ad absurdum. Euclid of Alexandria (mid-3rd – mid-4th centuries BCE) and Archimedes of Syracuse (c. 287 – c. 212 BCE) are two very early examples.

The earlier dialogues of Plato (424–348 BCE), relating the discourses of Socrates, raised the use of reductio arguments to a formal dialectical method (elenchus), also called the Socratic method. Typically, Socrates' opponent would make what would seem to be an innocuous assertion. In response, Socrates, via a step-by-step train of reasoning, bringing in other background assumptions, would make the person admit that the assertion resulted in an absurd or contradictory conclusion, forcing him to abandon his assertion and adopt a position of aporia. The technique was also a focus of the work of Aristotle (384–322 BCE). The Pyrrhonists and the Academic Skeptics extensively used reductio ad absurdum arguments to refute the dogmas of the other schools of Hellenistic philosophy.