Showing posts from April, 2017

Formal logic

Genesis 1:1 * describes the following logic Informally Premise P1: God exists. Premise P2: If P1 then "the universe is as old as the earth**". Conclusion C1: The universe is as old as the earth. Formally P1 → C1, P1        C1 This form of logic is called Modus Ponens. The truth of C1 doesn't imply the truth of P1 because there may be other explanations for C1. Lets look at the following classical example Premise P3: It rains Premise P4: If P3 then "the streets are wet". Conclusion C2: The streets are wet There are other possible explanations for wet streets: A cleaning crew just passed, there were games with water, the dikes were broken, etc ... However, we can say that, if the streets are not wet then it doesn't rain. Formally P3 → C2, ¬C2        ¬P3 This form of logic is called Modus Tollens and is the inverse of Modus Ponens. To return to Genesis 1:1. C1 is false and Modus Tollens applies. P1 → C1, ¬C1        ¬