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4. Formal Logic / B. Propositional Logic PL / 3. Truth Tables

[displaying logical relations in terms of true and false]

9 ideas
Truth tables give prior conditions for logic, but are outside the system, and not definitions [Tarski]
     Full Idea: Logical sentences are often assigned preliminary conditions under which they are true or false (often given as truth tables). However, these are outside the system of logic, and should not be regarded as definitions of the terms involved.
     From: Alfred Tarski (The Semantic Conception of Truth [1944], 15)
     A reaction: Hence, presumably, the connectives are primitives (with no nature or meaning), and the truth tables are axioms for their use? This opinion of Tarski's may have helped shift the preference towards natural deduction introduction and elimination rules.
Truth-tables are good for showing invalidity [Lemmon]
     Full Idea: The truth-table approach enables us to show the invalidity of argument-patterns, as well as their validity.
     From: E.J. Lemmon (Beginning Logic [1965], 2.4)
A truth-table test is entirely mechanical, but this won't work for more complex logic [Lemmon]
     Full Idea: A truth-table test is entirely mechanical, ..and in propositional logic we can even generate proofs mechanically for tautological sequences, ..but this mechanical approach breaks down with predicate calculus, and proof-discovery is an imaginative process.
     From: E.J. Lemmon (Beginning Logic [1965], 2.5)
Truth-tables are dubious in some cases, and may be a bad way to explain connective meaning [Dummett]
     Full Idea: It is arguable whether two-valued truth tables give correct meanings for certain sentential operators, and even whether they constitute legitimate explanations of any possible sentential operators.
     From: Michael Dummett (The Justification of Deduction [1973], p.294)
     A reaction: See 'Many-valued logic' for examples of non-binary truth tables. Presumably logicians should aspire to make their semantics precise, as well as their syntax.
Until the 1960s the only semantics was truth-tables [Enderton]
     Full Idea: Until the 1960s standard truth-table semantics were the only ones that there were.
     From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.10.1)
     A reaction: The 1960s presumably marked the advent of possible worlds.
Each line of a truth table is a model [Fitting/Mendelsohn]
     Full Idea: Each line of a truth table is, in effect, a model.
     From: M Fitting/R Mendelsohn (First-Order Modal Logic [1998], 1.6)
     A reaction: I find this comment illuminating. It is being connected with the more complex models of modal logic. Each line of a truth table is a picture of how the world might be.
Truth tables assume truth functionality, and are just pictures of truth functions [Sider]
     Full Idea: The method of truth tables assumes truth functionality. Truth tables are just pictures of truth functions.
     From: Theodore Sider (Logic for Philosophy [2010], 6.3)
In classical/realist logic the connectives are defined by truth-tables [Friend]
     Full Idea: In the classical or realist view of logic the meaning of abstract symbols for logical connectives is given by the truth-tables for the symbol.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007])
     A reaction: Presumably this is realist because it connects them to 'truth', but only if that involves a fairly 'realist' view of truth. You could, of course, translate 'true' and 'false' in the table to empty (formalist) symbols such a 0 and 1. Logic is electronics.
Boolean connectives are interpreted as functions on the set {1,0} [Walicki]
     Full Idea: Boolean connectives are interpreted as functions on the set {1,0}.
     From: Michal Walicki (Introduction to Mathematical Logic [2012], 5.1)
     A reaction: 1 and 0 are normally taken to be true (T) and false (F). Thus the functions output various combinations of true and false, which are truth tables.