Transcript Lecture XVI
LECTURE 16 THE MODAL ONTOLOGICAL ARGUMENT: PRELIMENARIES THE FAMOUS KANTIAN CRITICISM “EXISTENCE IS NOT A PREDICATE (PROPERTY, ATTRIBUTE)” THIS WOULD IMPLY THAT PREMISE (2) OF DESCARTES’ VERSION IS FALSE. PERFECTIONS ARE SUPPOSED TO BE ATTRIBUTES. FOR THE RECORD, I DO NOT THINK THAT THIS IS A GOOD CRITICISM OF THE ARGUMENT. BUT IT DOESN’T MATTER. WE HAVE ALREADY SHOWN THAT DESCARTES’ ARGUMENT IS DEFECTIVE A REACTION TO KANT’S CRITICISM: NECESSARY EXISTENCE IS AN ATTRIBUTE. SO WE CAN REFORMULATE USING ‘NECESSARY EXISTENCE.’ PROBLEM: THE RESULTING ARGUMENT STILL HAS THE EQUIVOCATION WE CRITICIZED. ANOTHER WAY OF CRITICIZING THE ARGUMENT: IF THIS ARGUMENT WORKED, SO WOULD ONE WITH ‘NEGMOUNT’ –CF. VAN INWAGEN. ANSELM’S ORIGINAL VERSION THE MONK GAUNILO (A CONTEMPORARY OF ANSELM) CRITICIZED ANSELM’S ARGUMENT IN THE SECOND WAY: IF THE PROOF WORKS FOR A PERFECT BEING, SO WOULD A PROOF FOR THE EXISTENCE OF A PERFECT ISLAND. BUT IT IS ABSURD TO THINK THAT A PERFECT ISLAND EXISTS. SO SOMETHING IS WRONG WITH ANSELM’S ARGUMENT. OTHER CRITICISMS OF ANSELM’S VERSION FOR AN EXCELLENT CRITICAL DISCUSSION OF ANSELM’S ORIGINAL VERSION (AND KANT’S CRITICISM’S) SEE ALVIN PLANTINGA, GOD AND OTHER MINDS MODALITY WE INTRODUCE THE PHILOSOPHICALLY USEFUL IDEA OF A PROPOSITION. A PROPOSITION IS THE SORT OF THING THAT IS APPROPRIATE TO BE THE MEANING OF A DECLARATIVE SENTENCE. DIFFERENT SENTENCES IN DIFFERENT LANGUAGES MAY EXPRESS THE SAME PROPOSITION. MOUNT EVEREST AGAIN “MOUNT EVEREST IS 8000 METERS HIGH.” “EL MONTE EVEREST ES OCHO MIL METROS DE ALTURA” “MOUNT EVEREST YN WYTH MILIWN METR UCHEL.” THESE THREE SENTENCES EXPRESS THE SAME PROPOSITION, EACH IN ITS RESPECTIVE LANGUAGE. “POSSIBLE WORLDS” A POSSIBLE WORLD MAY BE THOUGHT OF AS A COLLECTION OF PROPOSITIONS COMPLETELY DESCRIBING A WAY THE WORLD MIGHT HAVE BEEN. THERE CANNOT BE A CONTRADICTION OR IMPOSSIBILITY LURKING IN THE “STORY” (OR “SCENARIO”). POSSIBLE WORLDS ARE NOT OTHER PLANETS. THEY ARE COMPLETE “HISTORIES” OF A WAY THINGS MIGHT HAVE GONE. A USEFUL HEURISTIC WE MAY SAY THAT A PROPOSITION IS POSSIBLE IF THERE IS A POSSIBLE WORLD “IN WHICH IT WOULD BE TRUE.” WE MAY SAY THAT A PROPOSITION IS NECESSARY IF IT “WOULD BE TRUE IN EVERY POSSIBLE WORLD.” WE WILL USE “POSSIBLE WORLDS” SPARINGLY VAN INWAGEN’S EXPLICATION OF THE MODAL ONTOLOGICAL ARGUMENT USES POSSIBLE WORLDS EXTENSIVELY AND MAY BE DIFFICULT TO FOLLOW. WE EXPLAIN A VERSION WHICH IS A DESCENDANT OF CHARLES HARTSHORNE STATEMENT (EXTRA READING). A VALID MODAL PRINCIPLE: “MODAL MODUS PONENS (MMP)” NECESSARILY, IF P, THEN Q. POSSIBLY P. POSSIBLY Q. EXAMPLE “NECESSARILY, IF TODAY IS THURSDAY, THEN TOMORROW IS FRIDAY. “IT IS POSSIBLE THAT TODAY IS THURSDAY. HENCE, IT IS POSSIBLE THAT TOMORROW IS FRIDAY.” POSSIBLE WORLDS PICTURE NECESSARILY, IF P, THEN Q. POSSIBLY P POSSIBLY Q P IF P, THEN Q IF P, THEN Q IF P, THEN Q IF P, THEN Q IF P, THEN Q Q A LESS OBVIOUS MODAL PRINCIPLE: S5 IT IS POSSIBLE THAT P IS NECESSARY. P IS NECESSARY (S5) EXPLANATION: IN SOME POSSIBLE WORLD, P IS NECESSARY. BUT THE MODAL STATUS OF A PROPOSITION (NECESSARY, POSSIBLE, IMPOSSIBLE) IS THE SAME IN EVERY WORLD. IT DEPENDS SIMPLY ON THE INTRINSIC NATURE OF THE PROPOSITION. POSSIBLE WORLDS PICTURE NECESSARILY, P (1) IT IS POSSIBLE THAT THERE BE A PERFECT BEING. [Premise] (2) NECESSARILY, IF THERE IS SOMETHING THAT IS PERFECT, THEN NECESSARILY THERE IS SOMETHING THAT IS PERFECT. [Premise] (3) IF IT IS POSSIBLE THAT THERE BE A PERFECT BEING, THEN IS POSSIBLE THAT IT IS NECESSARY THAT THERE IS A PERFECT BEING. [From (2) by modal logic].