Logic and truth
- 1. Logic and Truth Rindang P. 121012173
- 2. • The study of logic Classical Greek world ( Aristotle ) • Logic the principle of valid argument and inference • Tools of logic help to represent sentence meaning
- 3. The example of Aristotle’s modus ponen (a type of argument in 3 steps) a. If Mark is not in the bar, then he is in the lounge. premises b. Mark is not in the bar. Modus Ponen c. Mark is in the lounge. conclusion If step a & b are TRUE, so step c is also TRUE
- 4. • Part of this study is concern for truth of statements and whether truth is preserved or lost by putting sentence into different patterns. • Truth correspondence with facts • Most part of this truth empirical/contingent
- 5. • The example of the truth or otherwise of sentence : My father was the first man to visit Mars. *depend on facts, if the fact is true, the sentence is true, otherwise is false. • The example of empirical truth : The earth revolves around the sun. *depend upon the facts of the universe Semantistics call sentence’s being TRUE or FALSE as truth value and call the facts as truth condition.
- 6. • By adding NOT, it will REVERSE its truth value Example : a. Your car has been stolen. b. Your car has not been stolen. If a is TRUE, b is FALSE. If a is FALSE, b is TRUE. • Logicians use a schema, logical form, where a lower case letter (p,q,r,etc) stands for the statements and special symbol for negation : -. THUS, Your car has been stolen p Your car has not been stolen. -p
- 7. THUS, Your car has been stolen p Your car has not been stolen. -p The effect of negation (-) on truth value of statement can be shown by a truth table, where T “true” F “false”