Combining Texts

Ideas for 'Writing the Book of the World', 'Axiomatic Theories of Truth' and 'Spheres of Justice'

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2 ideas

4. Formal Logic / E. Nonclassical Logics / 3. Many-Valued Logic
In Strong Kleene logic a disjunction just needs one disjunct to be true [Halbach]
     Full Idea: In Strong Kleene logic a disjunction of two sentences is true if at least one disjunct is true, even when the other disjunct lacks a truth value.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 18)
     A reaction: This sounds fine to me. 'Either I'm typing this or Homer had blue eyes' comes out true in any sensible system.
In Weak Kleene logic there are 'gaps', neither true nor false if one component lacks a truth value [Halbach]
     Full Idea: In Weak Kleene Logic, with truth-value gaps, a sentence is neither true nor false if one of its components lacks a truth value. A line of the truth table shows a gap if there is a gap anywhere in the line, and the other lines are classical.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 18)
     A reaction: This will presumably apply even if the connective is 'or', so a disjunction won't be true, even if one disjunct is true, when the other disjunct is unknown. 'Either 2+2=4 or Lot's wife was left-handed' sounds true to me. Odd.