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Use this tag for general questions about logic that are not categorizable under some more specific tag, like "mathematical logic", "informal logic", "classical logic", etc.
2
votes
2
answers
155
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Arguments Against Plural Quantification
What are some good arguments against taking plural logic, a slight extension of first order logic with plural quantification as a foundational logic? … The SEP article also mentions some results like the equi-interpretability of monadic second order logic and plural logic as justification for the ontological innocence of plural logic. …
2
votes
1
answer
155
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Rejecting the principle that any proposition can be meaningfully negated
Your argument in (1) that all logics have to be closed under negation
seems to rest on the assumption that a logic should consist of all
meaningful expressions in some context. …
0
votes
1
answer
526
views
Describing differences between "computational" and "non-computational" proofs
Let's call the resulting proof in our refinement logic-inspired system H. …
2
votes
1
answer
190
views
Are there modern approaches to logic that aren't *grounded* in math?
In fact, you may think what we are doing isn’t really
"logic" at all, but more philosophy of language, or even philosophy of
mind or epistemology. Why then call it logic? … It suggests but does not directly claim that conflating an application of logic and logic itself obscures some important and interesting ideas. …
1
vote
0
answers
30
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disjointness in logics with higher order plurals
Have disjoint and non-disjoint flavors of higher-order logic with plural quantifiers both been studied? …
0
votes
Approximately directed graph of logic types
The single, most important logic is classical first-order logic (henceforth FOL). … , dependence logic. …
35
votes
Accepted
How is the argument "I love all logic, but I don’t love deductive reasoning. Therefore, the ...
What kind of manipulation is valid formally changes from system to system (e.g. in intuitionistic logic vs classical logic). … Classical logic, however, doesn't give us the ability to talk about causality. …
4
votes
1
answer
234
views
How do you work with a non-classical metatheory?
I'm interested in nonclassical logic, particularly propositional logics because you only have one type of non-logical symbol. … The most powerful for propositional logics, in my opinion, is just translating formulas inductively into a classical first order logic with a single sort. …
2
votes
0
answers
210
views
What are the consequences of rejecting identity of indiscernibles
(c≠d)∧(P(c)↔P(d))
Are there any go-to paradoxes / counterintuitive results if we take (3) as an axiom in
a second-order logic system? …
1
vote
1
answer
296
views
Are there useful logics that reject disjunction introduction?
Here's a somewhat artificial example of a three-valued logic constructed not to admit disjunction introduction while still having fairly symmetrical truth tables and agreeing with classical logic when … Here's a three-valued logic that doesn't admit disjunction introduction, and has the connectives K (conjunction/koniunkcja), A (disjunction/alternatywa), and C (implication/implikacja). …
0
votes
1
answer
73
views
Non-equivalence of `i`-form and a claim of existence
In traditional logic, the following inference is valid
All As are Bs. AaB
----------------- -----
Some As are Bs. …
0
votes
Why is any sentence a logical consequence of a set of inconsistent premises?
I'll discuss classical propositional logic.
Let M (for "model") be an intepretation. We can make M just a set of variables that are true, e.g. {A, B, C} or similar. … This is a specialized topic within logic, but people do study systems of logic that are specifically designed to avoid certain paradoxes or counterintuitive behavior like consequences following from contradictory …
2
votes
Prove that if S tautological consequence of P, S tautological consequence of Q, then S tauto...
So, the conditional theorem below is correct.
P ⊢ S
Q ⊢ S
---------
P∨Q ⊢ S
The conditional theorem is only false if there's a case where the premises are true and conclusion is false.
And simi …
0
votes
Variant of free logic that accepts domain emptiness but rejects non-referring terms
The variant of free logic that permits domains to be empty, but rejects non-referring terms is simply first-order logic. … Some presentations of first-order logic allow the domain to be empty, others require it to be non-empty. …
0
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Help needed with predicate interpretations- Wilfrid Hodges logic
So, we want to encode the following sentence fragment in first-order logic:
nor may any true gentlemen be punished with shipping, unless his crime be very shameful, and his course of life vicious and …