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2+2 = not what you think

felipec.substack.com

Changing someone's mind is very difficult, that's why I like puzzles most people get wrong: to try to open their mind. Challenging the claim that 2+2 is unequivocally 4 is one of my favorites to get people to reconsider what they think is true with 100% certainty.

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No? So nobody in mathematics doubts the Zermelo–Fraenkel set theory axiomatic system?

Doubt about axioms is basically mathematical philosophy.

Who said an engineer should doubt 1+1=2?

So you agree doubt about everything is not reasonable in every field?

Doubt about axioms is basically mathematical philosophy.

So it's essential.

So you agree doubt about everything is not reasonable in every field?

Depends on what you mean by "doubt". If you mean <100% certainty, then no. If you mean 50% certainty, then yes.

So it's essential.

No it isn't. You will never encounter it in most math fields. Philosophy mostly is what you do when you aren't busy with concrete problems.

Depends on what you mean by "doubt".

What should an engineer do who needs to calculate 1+1 to design a bridge? I hold that anything but "answer 2 and move on" is wasting time that could be used to build a bridge.