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Small-Scale Question Sunday for June 16, 2024

Do you have a dumb question that you're kind of embarrassed to ask in the main thread? Is there something you're just not sure about?

This is your opportunity to ask questions. No question too simple or too silly.

Culture war topics are accepted, and proposals for a better intro post are appreciated.

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The terms “modus ponens” and “modus tollens” come from formal logic. They tell you how to deduce conclusions from statements.

Modus ponens says that if you know that A is true, and that B is true whenever A is true, then you can deduce that B is true. For instance: “If someone is a hunan, then he is mortal. Socrates is a human. Therefore, he is mortal.”

Conversely, modus tollens says that if you know that B is true whenever A is true, and you know that B is not true, then A is not true. “If someone is a human, then he is mortal. Zeus is immortal. Therefore, Zeus is not a human.”

The full expression extends these terms to the realm of politics and morality. For a naive culture war adjacent example: “Christianity says that gay sex is bad. Christianity is good. Therefore, gay sex is bad.” This is a sort of moral equivalent to modus ponens as described above. But, if you support gay rights, then you can do this in reverse: “Christianity says that gay sex is bad. Gay sex is good. Therefore, Christianity is bad.” This id the equivalent of modus tollens.

The expression thus can be viewed as saying “if you support a consequence because a preexisting belief of yours says that it’s good, then someone else could just as easily reject that consequence and say that your preexisting belief is bad.”