LECTURE 19
THE COSMOLOGICAL
ARGUMENT
CONTINUED
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
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.
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.
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.
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 (?!!).
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.)
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.
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.
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.
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.