In order to work along with the lectures, you'll find it useful to check out John Halpin's Logic Café: thelogiccafe.net/PLI/. This week we're working with Chapter Four.
Hi, you should stop teaching John Halpin’s interpretation of “unless” asap. It’s just outright wrong! For example, from the sentence “Ames is a politician unless Connors isn’t a politician”, one just cannot conclude (A v ~C). By doing so, one would allow ‘Ames being a politician’ AND ‘Connors not being a politician’. This option is specifically denied in the sentence. So, it should be (~A v C) which is equivalent to (A>C) , and consequenly also (~C> ~A). This interpretation is correct, giving the sentence following meanings: - If Ames is a politician, then we know Connors is also a politician (A>C) or - Connors being a politician is a necessary condition of Ames being a politician (A>C) or - Ames is a politician only if Connors is a politician (A>C) or - Ames is not a politician if Connors is not a politician (~C > ~A) -> (A>C) “We win unless the other team scores” is interpreted by Halpin as (W v S). Wrong! Again, W & S is an impossible scenario. A correct way to put it would be something like (~W v ~S)ꓥ(S v ~W) which is the same as (W>~S)ꓥ(~S>W), being equivalent to (W~S), and consequently also (~WS). Summa summarum: (X unless Y) = (X>~Y) Exception: If the outcomes are interrelated like in the previous example, then equivalence (X~Y) follows. That rule seems useful, unless someone finds an example that violates it (U>~E).
Hi Laura - Can't say I disagree. This is discussed, though, somewhere in the lectures. I can actually (at least sometimes) see why John chose to interpret "unless" this way. In the end, this disagreement allows some discussion -- which I think is profitable in the course -- about just how to choose interpretations for these terms. Anyway, thanks for the note. - Cheers, Jack
Thank you for your reply. I still can’t think of any situation where that would even remotely make sense (unless the exclusive type of ‘or’ is used). If we interpret the sentence ”we win unless the other team scores” as “W V S“ and if we have another premise “W” (or “S”), nothing can be deduced about the other team’s success. This is violating the whole beauty of ‘unless’ which leaves no room for such uncertainty. I can’t understand how Halpin’s view can be defended by anyone:) Even the truth table is against him; “(W&~S)V(~W&S)” and “WVS” just won’t match. Otherwise, I really enjoyed this lecture series, thank you!
Thank you for your clearification Laura, your input goes along with a feeling I get in some instances of the lectures - some of what is discussed seems to be taken for granted, though it can be merely subjective thoughts and intuitions of John - which are certainly valuable, but should be noted as such, hence the different way of interpertations of language, thoughts that could pop up with them, different starting points of solving a problem (without defining a precise format)etc. I get that the course shines with hints of philosophy, but when we go into the realm of the accurate, we need to be systematic - it's part of the deal :) Btw, have you been taking/teaching about these subjects?
In order to work along with the lectures, you'll find it useful to check out John Halpin's Logic Café: thelogiccafe.net/PLI/. This week we're working with Chapter Four.
Hi, you should stop teaching John Halpin’s interpretation of “unless” asap. It’s just outright wrong!
For example, from the sentence “Ames is a politician unless Connors isn’t a politician”, one just cannot conclude (A v ~C). By doing so, one would allow ‘Ames being a politician’ AND ‘Connors not being a politician’. This option is specifically denied in the sentence. So, it should be (~A v C) which is equivalent to (A>C) , and consequenly also (~C> ~A). This interpretation is correct, giving the sentence following meanings:
- If Ames is a politician, then we know Connors is also a politician (A>C) or
- Connors being a politician is a necessary condition of Ames being a politician (A>C) or
- Ames is a politician only if Connors is a politician (A>C) or
- Ames is not a politician if Connors is not a politician (~C > ~A) -> (A>C)
“We win unless the other team scores” is interpreted by Halpin as (W v S). Wrong! Again, W & S is an impossible scenario. A correct way to put it would be something like (~W v ~S)ꓥ(S v ~W) which is the same as (W>~S)ꓥ(~S>W), being equivalent to (W~S), and consequently also (~WS).
Summa summarum:
(X unless Y) = (X>~Y)
Exception: If the outcomes are interrelated like in the previous example, then equivalence (X~Y) follows.
That rule seems useful, unless someone finds an example that violates it (U>~E).
Hi Laura - Can't say I disagree. This is discussed, though, somewhere in the lectures. I can actually (at least sometimes) see why John chose to interpret "unless" this way. In the end, this disagreement allows some discussion -- which I think is profitable in the course -- about just how to choose interpretations for these terms. Anyway, thanks for the note. - Cheers, Jack
Thank you for your reply. I still can’t think of any situation where that would even remotely make sense (unless the exclusive type of ‘or’ is used). If we interpret the sentence ”we win unless the other team scores” as “W V S“ and if we have another premise “W” (or “S”), nothing can be deduced about the other team’s success. This is violating the whole beauty of ‘unless’ which leaves no room for such uncertainty. I can’t understand how Halpin’s view can be defended by anyone:) Even the truth table is against him; “(W&~S)V(~W&S)” and “WVS” just won’t match. Otherwise, I really enjoyed this lecture series, thank you!
Thank you for your clearification Laura, your input goes along with a feeling I get in some instances of the lectures - some of what is discussed seems to be taken for granted, though it can be merely subjective thoughts and intuitions of John - which are certainly valuable, but should be noted as such, hence the different way of interpertations of language, thoughts that could pop up with them, different starting points of solving a problem (without defining a precise format)etc.
I get that the course shines with hints of philosophy, but when we go into the realm of the accurate, we need to be systematic - it's part of the deal :)
Btw, have you been taking/teaching about these subjects?
@@jacksanders2611
Jack thank you very much for the content, are you John's relative? To be honest I thought these were your lectures😅