Hello! I'd like to ask about syllogisms. I have a particular problem when understanding this certain syllogism:
Some girls are single. Some girls are sad. Therefore, some girls are single and sad.
While I think it is valid, I cannot fully make an accurate explanation as to why it is. Hoping somebody could help me. Thanks!
I have recently compared two philosophy texts which are very very close in material they present: A Concise Introduction to logic 12th edition by Patrick Hurley and Introduction to Logic by Irving Copi & Carl Cohen 12th edition. I have a question about the logical Equivalence Rule Material Implication which states where ever P imples Q appears one can substitute Not P or Q and vice versa. I noticed if Not P or Q is Implicated the NOT is always on the left hand side. There is no instance of Q or Not P and the rule Material Implication being applied.
My question is if I am given "Q or Not P" can I apply Material Implication as written or must I commutate "Q or Not P" to get "Not P or Q" and then use the Material Implication rule? It seems all is done to avoid using material implication with a negative disjunct on the right hand side. What is the deal with that?
In other words, Would I get false conclusions if I deduce Q or Not P as Not Q or Not P? I am correct in guessing this may be the case? I...
Recently I got a question for a philosophy class on how the following set of statements is consistent: "All dragons love Katy Perry. All dragons hate Katy Perry." And we have to think about how to explain that this is consistent. I'm struggling to understand how to make that explanation.
I've come across what appears intersecting and incompatible logic systems within academia (and society).
System one is what I call analytic logic: the merit of your argument or opinion is completely independent of your immutable characteristics. (Like MJ says, it doesn't matter if you're black or white).
If you dismiss the merit of an argument by attacking the person who made it, you've committed a logical fallacy. The peer review process in academia avoids this potential by hiding the author's identity from reviewers. The argument or study is judged on its own merit.
I call system two Identitarianism (some call it Neo-Marxism or Intersectionalism). With these rules, your ethnicity(ies), gender, and sexual orientation (etc.) are in play. Some people have more (and others less) merit because of their immutable characteristics.
System two seems backwards but the rationale goes as follows:
"Oppressed" groups (POC, women, trans people, gay/lesbian, poor people, etc) have access to ...
(1) the norms,...
This is a follow up to a question answered by Dr. Maitzen on December 31 2020.
The statement really was “Only if A, then B”. It came up on a test question that asked the following:
“If A, then B” and “Only if A, then B” are logically equivalent. True or false?
The answer is ‘false’, apparently. I reasoned that “Only if A, then B” is maybe like saying “Necessarily: if A, then B”, and this is clearly different from saying simply “If A, then B”. But I’m not sure. Any chance you might be able to help me see why “If A, then B” and “Only if A, then B” aren’t equivalent? Clearly they say different things, but I’m just not sure how to put my finger on the difference.
I really appreciate the help. Thank you again.
I'm confused about the nature of antecedents and conditionals like: (i) "Only if A, then B".
I was told in my logic class that antecedents are always sufficient conditions and consequents are always necessary conditions. But if that's the case, then the antecedent in (i) "Only if A" is a sufficient condition. Particularly a sufficient condition for B. But saying "Only if A, then B" means that A is a necessary condition for B as well. So it appears that the antecedent in (i) is both a sufficient and necessary condition. But that doesn’t seem right, given that (i) is equivalent to (ii) If B, then A. And this means A is only a necessary but not a sufficient condition for B.
Option 1: Maybe antecedents only are sufficient conditions in simple conditionals like (iii) “If A, then B”; but they aren’t sufficient conditions in conditionals like "Only if A, then B". That might be right.
Option 2: On the other hand, we might say "Only if A" just seems to be an antecedent but isn't really. That would...
Let ‘B’= to be; let ‘~B’=not to be.
P1: B v ~B
P2 is the negation of the left disjunct in P1, not the affirmation of the right disjunct in P1.
P1: To be or not to be.
P2: Not to be.
C: Not to be.
It seems to me that, argumentatively, there’s a difference between affirming ‘not to be’, the right disjunct, and negating ‘to be’, the left disjunct. It just happens that, in this case, what’s affirmed and what’s negated are logically equivalent. Is there a convention for conveying that argumentative difference? Also, can you recommend any articles or books where I can learn more about issues like this?
Thank you very much :)
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