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and or conditional reversal
Posted: Tue Mar 20, 2012 9:02 pm
by Br3v
If x and y > z
Reversal of this would be:
If not z > not x or not y
Correct?
Now, could it be true that not z allows for both not x and not y? Or does not z only mean not x or not y but both not x and not y is impossible?
Re: and or conditional reversal
Posted: Tue Mar 20, 2012 9:03 pm
by Br3v
In other words if we have
x and y > z
Can this exist?
Not z > not x and not y
Re: and or conditional reversal
Posted: Tue Mar 20, 2012 9:08 pm
by lovejopd
Yes, generally "or" is inclusive, which include "both" unless it is stated 'not both' in Game
1. A or B can mean 3 things
1. Only A(O)
2. Only B(O)
3. A and B(O)
NOT
4. nothing (X)
2. A or B(but not both) mean 2 things
1. Only A(O)
2. Only B(O)
NOT
3. A and B (X)
4. Nothing (X)
1. A --> B or C
~B AND ~C --> ~A
2. A --> B and C
~B or ~C --> ~A
Simply pay attention to the transition from OR to AND or vice versa when doing contrapositive
Hope this helps!
Re: and or conditional reversal
Posted: Tue Mar 20, 2012 9:11 pm
by Br3v
lovejopd wrote:Yes, generally "or" is inclusive, which include "both" unless it is stated 'not both' in Game
1. A or B can mean 3 things
1. Only A(O)
2. Only B(O)
3. A and B(O)
NOT
4. nothing (X)
2. A or B(but not both) mean 2 things
1. Only A(O)
2. Only B(O)
NOT
3. A and B (X)
4. Nothing (X)
1. A --> B or C
~B AND ~C --> ~A
2. A --> B and C
~B or ~C --> ~A
Simply pay attention to the transition from OR to AND or vice verse when doing contrapositive
Hope this helps!
It did thanks
Re: and or conditional reversal
Posted: Tue Mar 20, 2012 9:13 pm
by kaiser
Unless told otherwise, the word "or" doesn't mean just one or the other in a mutually exclusive way
X and Y --> Z
Not Z --> Not X or Not Y (or both)
Whenever you write "or", you can just think of it as having the term "or both" at the end. If you have neither X nor Y, then of course the term "not X or not Y" is satisfied.
Re: and or conditional reversal
Posted: Tue Mar 20, 2012 9:31 pm
by Geetar Man
Brev,
Here is a thread I made that is relevant to your question.
http://www.top-law-schools.com/forums/v ... 6&t=180664
HTH.
Re: and or conditional reversal
Posted: Wed Mar 21, 2012 9:39 am
by Easy-E
kaiser wrote:Unless told otherwise, the word "or" doesn't mean just one or the other in a mutually exclusive way
X and Y --> Z
Not Z --> Not X or Not Y (or both)
Whenever you write "or", you can just think of it as having the term "or both" at the end. If you have neither X nor Y, then of course the term "not X or not Y" is satisfied.
Yepp, unless explicitly state, "or" is inclusive. Basically what you can take away from the contrapositive of kaiser's example is that if you don't have Z, then you cannot have both X and Y occurring, but one of the two could. That was probably redundant, but HTH.