Questions pertaining to logical constructs

learn more… | top users | synonyms

12
votes
5answers
8k views

Does “either A or B ” preclude “both A and B”?

In mathematics, "A or B" includes "A and B". Does "either" mean "A or B but not (A and B)" or does it include the possibility of "A and B"? The context might be mathematics, formal logic or ordinary ...
18
votes
7answers
6k views

“All that is gold does not glitter”

"All that is gold does not glitter" is the first line of a poem from the Lord of the Rings and it's supposed to mean "not all gold glitters" but I'm struggling to see how this can be deduced. If all ...
9
votes
5answers
7k views

“If” vs “Only if” vs “If and only if”

If I said: Yell only if I fall. Would the person have to yell once I fell? Sources of confusion Wikipedia This guy
1
vote
3answers
185 views

How do definitions of words imbue meaning? [closed]

How do definitions of words imbue meaning? To give you a gist of what I try to discover, I'll define a collection of sets of words and show that their intersection contains all 'circular defined' ...
7
votes
1answer
2k views

Difference between “subsequently” and “consequently”?

When studying and reading course material in "softer" sciences that are descriptive the word "subsequently" appears in a way like "and subsequently" ...what does it mean, disctinct from "consequently" ...
6
votes
5answers
1k views

Can I say “We don't must”, any alternative using a modal verb if I can't?

Let me explain. Suppose someone says "We must play a game now". I disagree, but only on that we have to do it. I shouldn't answer "We must not" because I would be saying that the game is not to be ...
4
votes
3answers
939 views

'Therefore' in an illogical logic sense

I have a co-worker that is always saying "Therefore, A B C" when the "A B C" isn't a conclusion from any sort of deductive reasoning. For example, Me: ... thus, that's how it works. Her: I ...