Which one of the following is an acceptable selection of fish and plants for the aquarium?
halesJuly 12, 2019
Neither/Nor
In the diagram set up Neither/Nor is diagramed as G ->not H and not y. Do we have a rule for neither nor that leads us to do this? Is this something I should remember to do with neither nor?
In my set up I diagramed it in two separate statements:
G -> not H
G-> not Y
(with the contrapositives of all the statements)
Replies
Create a free account to read and
take part in forum discussions.
combines both of those statements into one diagram, so it's easier to see what's going on. Your diagram and this one both mean the same thing, it's just that the one used in the explanation combines both rules so that they're easier to read and keep track of.
Does this make sense? Let us know if you have any other questions!
shafieiavaAugust 30, 2019
I'm having trouble understanding the deduction the instructor makes from this rule. How would we know that G and H are not both from this rule?
IrinaAugust 30, 2019
@shafieiava,
It is actually one of the rules of inference.
neither H nor Y can be diagrammed as:
~ (H v Y)
The rule of inference, known as De Morgan's Law, tells us that this statement is equivalent to:
~H & ~Y
We can thus make an inference that:
G -> ~(H v Y) is the same as: G -> ~ H & ~Y
Even if you forget the rule, you could make the same inference using natural language. Neither..nor..always means that neither of these conditions could be true, or both must be false.
For example:
Dogs can neither read nor write.
We understand this sentence to mean that dogs cannot read AND dogs cannot write. Both - can read and can write - must be false.
Does that make sense?
Let me know if you have any further questions.
jbenav246@gmail.comJanuary 11, 2021
When I wrote this rule, I wrote it as G-> not H or not Y but the instructor wrote it as G-> not H and not Y.... is "nor" considered "and" or "or"?
