1. LECTURE 19 THE COSMOLOGICAL ARGUMENT CONTINUED

2. THE QUANTUM MECHANICAL OBJECTION DEPENDS UPON A PARTICULAR INTERPRETATION WE MIGHT REASONABLY SUSPEND JUDGMENT ON THE QUESTION AS TO WHETHER OR NOT MODERN PHYSICS CONTRADICTS THE PRINCIPLE OF SUFFICIENT REASON

3. A PHILOSOPHICAL OBJECTION TO THE PRINCIPLE OF SUFFICIENT REASON VAN INWAGEN THINKS THAT THE PRINCIPLE OF SUFFICIENT REASON IMPLIES THAT ALL TRUTHS ARE NECESSARY. THIS LATTER IS VERY IMPLAUSIBLE. HENCE, HE CONCLUDES, THE PRINCIPLE OF SUFFICIENT REASON SHOULD BE REJECTED.

4. THE ARGUMENT IS A BIT SUBTLE CONSIDER THE POSSIBLE WORLD A WHICH IS THE ACTUAL WORLD. THAT A IS THE ACTUAL WORLD IS CERTAINLY A CONTINGENT PROPOSITION – SINCE IT IMPLIES MANY CONTINGENT PROPOSITIONS (E.G. THAT THE EIFFEL TOWER IS IN PARIS). SINCE THE PROPOSITION THAT A IS THE ACTUAL WORLD IS TRUE, IT MUST HAVE A SUFFICIENT REASON, SAY S.

5. WHAT MUST S BE LIKE? SINCE S IS SUPPOSED TO BE AN EXPLANATION OF THE FACT THAT A IS THE ACTUAL WORLD, IT MUST LOGICALLY IMPLY ALL CONTINGENT PROPOSITIONS. SUPPOSE THAT S IS CONTINGENT. THE FACT THAT A IS THE ACTUAL WORLD MUST IMPLY THAT S IS TRUE, OTHERWISE S MIGHT BE TRUE OF SOME OTHER POSSIBLE WORLD. THEREFORE, THAT A IS THE ACTUAL WORLD AND S MUST LOGICALLY IMPLY EACH OTHER.

6. SO S AND THE FACT THAT A IS THE ACTUAL WORLD MUST LOGICALLY IMPLY EACH OTHER THIS MEANS THAT S AND THE PROPOSITION THAT A IS THE ACTUAL WORLD ARE BASICALLY THE SAME PROPOSITION. BUT A PROPOSITION CANNOT EXPLAIN ITSELF. WE CONCLUDE THAT IF S EXPLAINS THE FACT THAT A IS THE ACTUAL WORLD, IT MUST BE A NECESSARY PROPOSITION. BUT THEN EVERYTHING TRUE IN THE ACTUAL WORLD MUST BE NECESSARY (?!!).

7. ADMITTEDLY THIS IS A COMPLEX PHILOSOPHICAL ARGUMENT VAN INWAGEN OBSERVES (IN A FOOTNOTE) THAT THE ARGUMENT DEPENDS UPON THE ASSUMPTION THAT LOGICALLY EQUIVALENT PROPOSITIONS ARE IDENTICAL, OR AT LEAST THAT A PROPOSITION CANNOT EXPLAIN A FACT TO WHICH IT IS LOGICALLY EQUIVALENT. (FOR THE RECORD, I BELIEVE THAT THIS LATTER CLAIM IS FALSE. BUT DON’T TAKE MY WORD FOR IT.)

8. THOMAS AQUINAS’ VERSION OF THE COSMOLOGICAL ARGUMENT SAINT THOMAS AQUINAS REJECTED THE ONTOLOGICAL ARGUMENT BUT CLAIMED THAT THE EXISTENCE OF GOD CAN BE PROVED IN FIVE WAYS. WE CONSIDER ONLY THE THIRD WAY, WHICH PURPORTS TO PROVE THE EXISTENCE OF A NECESSARY BEING.

9. AQUINAS’ THIRD WAY (1)THERE ARE AT PRESENT CONTINGENTLY EXISTING BEINGS. (2)IF A THING CONTINGENTLY EXISTS, THEN AT SOME TIME IT FAILS TO EXIST. (3) IF EVERYTHING CONTINGENTLY EXISTS, THEN AT SOME TIME NOTHING EXISTED. (4) IF NOTHING EXISTS AT SOME TIME, THEN NOTHING EXISTS AT ANY SUBSEQUENT TIME.

10. CONCLUSION (5) IF EVERYTHING CONTINGENTLY EXISTS, THEN NOTHING EXISTS NOW. THIS CONTRADICTS PREMISE (1). THEREFORE, (6) NOT EVERYTHING CONTINGENTLY EXISTS, I.E., SOMETHING NECESSARILY EXISTS.

11. A QUANTIFIER ERROR? IN GENERAL, FROM THE FACT THAT FOR EVERY X THERE IS A Y SUCH THAT …X…Y…, IT DOESN’T FOLLOW THAT THERE IS A Y SUCH THAT FOR EVERY X …X…Y,…. IN SYMBOLISM:  x  y(…x…y…) DOES NOT LOGICALLY IMPLY  y  x(…x…y…). AQUINAS’ ARGUMENT SEEMS TO MAKE THIS MISTAKE.