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Questions tagged [medieval-logic]

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14 votes
2 answers

How do I use the "Barbara, Celarent, … etc." mnemonic?

Medieval logicians memorized this most famous logic mnemonic: Barbara, Celarent, Darii, Ferio ← direct first figure Baralipton, Celantes, Dabitis, Fapesmo, Frisesomorum ← indirect first figure Cesare,...
Geremia's user avatar
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4 votes
1 answer

Did William of Soissons prove the law of explosion in the 12th century?

In the 12th century, William of Soissons attempted to prove that any proposition can be inferred from a contradiction. I've adapted his proof into a logical system I'm more familiar with: Let E ...
N. Bar's user avatar
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4 votes
1 answer

How do medieval theories of reference account for *entia rationis* (objects of thought)?

The medieval theories of logic generally hold, at least as represented in the brilliant work of Thomas Aquinas, that non-existent being can be said of existent being because non-existent being can be ...
Bombadil's user avatar
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3 votes
1 answer

Who first said: "Never deny, seldom affirm, always distinguish"?

In the context of medieval scholastic disputations, what is the origin of the axiom "Never deny, seldom affirm, always distinguish" ("Numquam negare, raro affirmare, semper distinguere&...
Geremia's user avatar
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3 votes
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Are analogical middle terms sufficient for a valid demonstration?

William A. Wallace, O.P., in “Thomism and the Quantum Enigma,” The Thomist 61 (1997): 455–468, claims that analogical middle terms are sufficient for a valid demonstration and that this is a ...
Geremia's user avatar
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2 votes
1 answer

Where does Aquinas get his "logical-metaphysical presuppositions"?

In the Summa, Aquinas frequently invokes (for lack of a better term) certain "logical-metaphysical presuppositions." Here are two examples drawn from I-II, qq. 90-91: "that which is ...
Doubt's user avatar
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1 vote
3 answers

"Animal is human": human is not among the five predicables

I'm asking about the proposition "Animal is human" (as opposed to "Human is an animal"). All predicates are amongst the five predicables, i.e. they are either essential or ...
Shahram's user avatar
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