Post History
#2: Post edited
by
Peter Taylor
·
2021-08-05T07:27:43Z (over 3 years ago)
A proposed edit tried to improve the typography with nbsp; this is a better fix
- Harry Gensler. [*Introduction to Logic*](https://www.amazon.com/Introduction-Logic-Harry-J-Gensler/dp/1138910597) (2017 3 ed). p 169.
>“Unless” is also equivalent to “if not”; so we also could use “(∼B ⊃ D) (“If you- don’t breathe, then you’ll die”).”
- Nicholas JJ Smith, [*Logic: The Laws of Truth*](https://www.amazon.com/Logic-Truth-Nicholas-J-J-Smith/dp/0691151636) (2012). p 115.
- >The statement “P unless Q” means that if Q is not true, P is true—so we
- translate it as $¬ \, Q→P$.
- Using solely the original meaning of "unless" below, please expound why? How does definition 1 below ≡ if not? I know that definition 1 is obsolete, but I'm interested in the etymology. [*OED* Third Edition, June 2017](http://www.oed.com/view/Entry/215075). [Screenshot](https://i.stack.imgur.com/iZLrR.jpg).
- > †**A.** adv. Only in conjunctional phrases followed by _than_ or _that_.
- >
- >1. Forming a conjunctional phrase introducing a case in which an exception to a preceding negative statement (expressed or implied) will or may exist: (not) on a less or lower condition, requirement, etc., _than_ (what is specified). _Obsolete_.
- Harry Gensler. [*Introduction to Logic*](https://www.amazon.com/Introduction-Logic-Harry-J-Gensler/dp/1138910597) (2017 3 ed). p 169.
- >“Unless” is also equivalent to “if not”; so we also could use “$({\sim}B \supset D)$ (“If you
- don’t breathe, then you’ll die”).”
- Nicholas JJ Smith, [*Logic: The Laws of Truth*](https://www.amazon.com/Logic-Truth-Nicholas-J-J-Smith/dp/0691151636) (2012). p 115.
- >The statement “P unless Q” means that if Q is not true, P is true—so we
- translate it as $¬ \, Q→P$.
- Using solely the original meaning of "unless" below, please expound why? How does definition 1 below ≡ if not? I know that definition 1 is obsolete, but I'm interested in the etymology. [*OED* Third Edition, June 2017](http://www.oed.com/view/Entry/215075). [Screenshot](https://i.stack.imgur.com/iZLrR.jpg).
- > †**A.** adv. Only in conjunctional phrases followed by _than_ or _that_.
- >
- >1. Forming a conjunctional phrase introducing a case in which an exception to a preceding negative statement (expressed or implied) will or may exist: (not) on a less or lower condition, requirement, etc., _than_ (what is specified). _Obsolete_.
#1: Initial revision
by
PSTH
·
2020-11-10T07:30:40Z (almost 4 years ago)
Why does “unless” mean “if not”?
Harry Gensler. [*Introduction to Logic*](https://www.amazon.com/Introduction-Logic-Harry-J-Gensler/dp/1138910597) (2017 3 ed). p 169. >“Unless” is also equivalent to “if not”; so we also could use “(∼B ⊃ D) (“If you don’t breathe, then you’ll die”).” Nicholas JJ Smith, [*Logic: The Laws of Truth*](https://www.amazon.com/Logic-Truth-Nicholas-J-J-Smith/dp/0691151636) (2012). p 115. >The statement “P unless Q” means that if Q is not true, P is true—so we translate it as $¬ \, Q→P$. Using solely the original meaning of "unless" below, please expound why? How does definition 1 below ≡ if not? I know that definition 1 is obsolete, but I'm interested in the etymology. [*OED* Third Edition, June 2017](http://www.oed.com/view/Entry/215075). [Screenshot](https://i.stack.imgur.com/iZLrR.jpg). > †**A.** adv. Only in conjunctional phrases followed by _than_ or _that_. > >1. Forming a conjunctional phrase introducing a case in which an exception to a preceding negative statement (expressed or implied) will or may exist: (not) on a less or lower condition, requirement, etc., _than_ (what is specified). _Obsolete_.