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Single Idea 19110

[filed under theme 5. Theory of Logic / K. Features of Logics / 10. Monotonicity ]

Full Idea

In classical logic, Monotony follows immediately from the nature of the relation |=, for Γ |= φ holds precisely when φ is true on every interpretation on which all sentences in Γ are true.

Gist of Idea

In classical logic the relation |= has Monotony built into its definition

Source

G. Aldo Antonelli (Non-Monotonic Logic [2014], 1)

Book Ref

'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.2


A Reaction

That is, semantic consequence (|=) is defined in terms of a sentence (φ) always being true if some other bunch of sentences (Γ) are true. Hence the addition of further sentences to Γ will make no difference - which is Monotony.


The 10 ideas from 'Non-Monotonic Logic'

Reasoning may be defeated by new premises, or by finding out more about the given ones [Antonelli]
In classical logic the relation |= has Monotony built into its definition [Antonelli]
Cautious Monotony ignores proved additions; Rational Monotony fails if the addition's negation is proved [Antonelli]
Weakest Link Principle: prefer the argument whose weakest link is the stronger [Antonelli]
Should we accept Floating Conclusions, derived from two arguments in conflict? [Antonelli]
You can 'rebut' an argument's conclusion, or 'undercut' its premises [Antonelli]
Non-monotonic core: Reflexivity, Cut, Cautious Monotonicity, Left Logical Equivalence, Right Weakening [Antonelli]
We can rank a formula by the level of surprise if it were to hold [Antonelli]
People don't actually use classical logic, but may actually use non-monotonic logic [Antonelli]
We infer that other objects are like some exceptional object, if they share some of its properties [Antonelli]