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13342
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Carnap defined consequence by contradiction, but this is unintuitive and changes with substitution [Tarski on Carnap]
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Full Idea:
Carnap proposed to define consequence as 'sentence X follows from the sentences K iff the sentences K and the negation of X are contradictory', but 1) this is intuitively impossible, and 2) consequence would be changed by substituting objects.
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From:
comment on Rudolph Carnap (The Logical Syntax of Language [1934], p.88-) by Alfred Tarski - The Concept of Logical Consequence p.414
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A reaction:
This seems to be the first step in the ongoing explicit discussion of the nature of logical consequence, which is now seen by many as the central concept of logic. Tarski brings his new tool of 'satisfaction' to bear.
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13251
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Each person is free to build their own logic, just by specifying a syntax [Carnap]
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Full Idea:
In logic, there are no morals. Everyone is at liberty to build his own logic, i.e. his own form of language. All that is required is that he must state his methods clearly, and give syntactical rules instead of philosophical arguments.
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From:
Rudolph Carnap (The Logical Syntax of Language [1934], §17), quoted by JC Beall / G Restall - Logical Pluralism 7.3
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A reaction:
This is understandable, but strikes me as close to daft relativism. If I specify a silly logic, I presume its silliness will be obvious. By what criteria? I say the world dictates the true logic, but this is a minority view.
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23216
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The brain is not passive, and merely processing inputs; it is active, and intervenes in the world [Cobb]
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Full Idea:
A number of scientists are now realising that, by viewing the brain as a computer that passively responds ot inputs and processes data, we forget that it is an active organ, part of the body intervening in the world.
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From:
Matthew Cobb (The Idea of the Brain [2020], Intro)
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A reaction:
I like any idea which reminds us that nature is intrinsically active, and not merely passive. Laws are in nature, not imposed on it. My preferred ontology, based on powers as fundamental, applies to the brain, as well as to physics. No free will needed.
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