LECTURE 25DESCARTES’S

ARGUMENT AND A LEIBNIZIAN

ARGUEMENT

DESCARTES’S ARGUMENT AGAINST PHYSICALISM (FOR DUALISM)

ARGUMENTS FOR DUALISM

“DESCARTES’ ARGUMENT”I CAN CONCEIVE OF THERE BEING

NO PHYSICAL BODIES.I CANNOT CONCEIVE THAT I DO NOT

EXIST.THEREFORE:I AM NOT A PHYSICAL BODY.

A LOGICAL PRINCIPLE

THE INDISCERNIBILITY OF IDENTICALS OR BETTER: THE DISTINCTNESS OF DISCERNIBLES

(DD) FOR ANY PROPERTY F AND ANY THINGS X AND Y, IF X HAS F AND Y DOES NOT, THEN X IS NOT IDENTICAL WITH Y.

THIS PRINCIPLE DD SEEMS UNIMPEACHABLE

IF X AND Y ARE THE VERY SAME THING (NOT JUST SIMILAR OR EXACTLY ALIKE), THEN ANYTHING THAT IS TRUE OF X IS TRUE OF Y (THAT IS, X).

IN LOGICAL SYSTEMS IT USUALLY IS CALLED “THE SUBSITUTIVITY OF IDENTICALS.”

NEVERTHELESS, THERE SEEMS TO BE SOMETHING WRONG WITH THE

ARGUMENT• COMPARE:• (1) I CAN CONCEIVE OF BATMAN NOT

EXISTING AND AT THE SAME TIME BRUCE WAYNE EXISTING.

• (2) I CANNOT CONCEIVE OF BRUCE WAYNE EXISTING AND AT THE SAME TIME BRUCE WAYNE NOT EXISTING.

THEREFORE:

(3) SO BATMAN HAS A PROPERTY THAT BRUCE WAYNE DOES NOT.

THEREFORE (BY DD)(4) BATMAN IS NOT BRUCE WAYNE.???!!!

VAN INWAGEN’S DIAGNOSIS

ACCORDING TO VAN INWAGEN, THE PROBLEM IS THAT THE PHRASE”

“…CAN BE CONCEIVED BY ME NOT TO EXIST”

DOES NOT EXPRESS (DENOTE, DESIGNATE) A PROPERTY.

A TEST FOR EXPRESSING A PROPERTY

CONSIDER A SENTENCE CONTAINING A PROPER NAME (OR OTHER DESIGNATOR OF AN INDIVIDUAL) AND REPLACE THE NAME BY THE VARIABLE ‘X’.

“OBAMA IS PRESIDENT”“X IS PRESIDENT”“ANDERSON IS A PHILOSOPHER”“X IS A PHILOSOPHER”

CALL THE RESULTING EXPRESSION A “LOGICAL PREDICATE”

THE TEST: A LOGICAL PREDICATE EXPRESSES (DENOTES, SIGNIFIES, CORRESPONDS TO) A PROPERTY ONLY IF THE RESULTS OF REPLACING ‘X’ BY TWO DIFFERENT DESIGNATIONS OF THE SAME INDIVIDUAL ARE BOTH TRUE OR BOTH FALSE.

TRY:“COMMISIONER GORDON KNOWS THAT X IS

BATMAN.”

THE LOGICAL PREDICATE IN DESCARTES’ ARGUMENT

“X CAN BE CONCEIVED BY ME NOT TO EXIST”CONSIDER THE TWO DESIGNATORS:“THE INSTRUCTOR OF PHIL 100E (S 2014)”“I”BOTH OF THESE DESIGNATE ME. BUT THE

LOGICAL PREDICATE FAILS THE TEST. (WHY? A VERY INTERESTING QUESTION. CF. PHILOSOPHY OF LANGUAGE).

SOME PREDICATES INVOLVE CONCEPTS OF THINGS

HERE IS ONE POSSIBLE EXPLANATION OF WHY THE DIFFERENCE OF DISCERNIBLES CANNOT BE APPLIED TO CERTAIN PREDICATES: THE PREDICATE AREN’T SIMPLY ABOUT A THING, BUT ARE ALSO SENSITIVE TO THE CONCEPT INVOLVED. CONSIDER: “JONES BELIEVES THAT THE BANK ROBBER IS A CROOK.” (TRUE)

SUPPOSE THE BANK ROBBER WAS DISGUISED AND WAS IN FACT THE

PRESIDENT OF THE BANK“JONES BELIEVES THAT X IS A CROOK” IS A LOGICAL PREDICATE BUT SUBSTITUTING A DESIGNATING TERM IN FOR “X” MAY GIVE A DIFFERENT RESULT DEPENDING ON THE CONCEPT IT EXPRESSES: “JONES BELIEVES THAT THE BANK PRESIDENT IS A CROOK” (FALSE)

SUCH CONTEXTS ARE CALLED “INTENSIONAL CONTEXTS”

MANY PSYCHOLOGICAL VERBS GIVE RISE TO SUCH CONTEXTS (CONTEXTS WHERE THE SUBSTITUTION TEST FAILS):BELIEVES, KNOWS, WONDERS WHETHER, DESIRES, SPECULATES, CONJECTURES, TRIES,… .ALSO MODAL NOTIONS: NECESSARILY, POSSIBLY, IT IS IMPOSSIBLE THAT, IT IS CONTINGENT THAT, ENTAILS,…. .

IT IS FAIR TO SAY THAT THE RESULTING LOGICAL PREDICATES DO NOT SIMPLY

EXPRESS PROPERTIES“COMMISIONER GORDON KNOWS THAT X IS BATMAN” DOES NOT SIMPLY EXPRESS A PROPERTY OF WHATEVER IS DESIGNATED BY THE TERM PUT IN FOR “X”. “BATMAN” AND “BRUCE WAYNE” GIVE DIFFERENT RESULTS. THIS LOGICAL PREDICATE EXPRESSES A PROPERTY OF A THING CONCEIVED IN A CERTAIN WAY.

BACK TO DESCARTES’S ARGUMENT

I PERHAPS CANNOT CONCEIVE OF MYSELF OF AS NOT PRESENTLY EXISTING. I CAN CONCEIVE OF MY BODY AS NOT PRESENTLY EXISTING. BUT “MYSELF” AND “MY BODY” MAY BOTH DESIGNATE ME – CONCEIVED IN DIFFERENT WAYS.WHATEVER THE EXACT EXPLANATION OF THE LOGICAL ERROR, THE ARGUMENT DOES NOT SEEM TO BE VALID.

GOTTFRIED WILHELM VON LEIBNIZ

A LEIBNIZIAN ARGUMENT AGAINST PHYSICALISM

(1) IT IS IMPOSSIBLE THAT PHYSICAL THINGS SHOULD BE CAPABLE OF THOUGHT AND PERCEPTION.

(2) I AM CAPABLE OF THOUGHT AND PERCEPTION.

THEREFORE:(3) I AM NOT A PHYSICAL THING

IT SEEMS IMPOSSIBLE TO IMAGINE HOW THOUGHT AND PERCEPTION COULD BE PRODUCED BY SOMETHING PHYSICAL

• LEIBNIZ’S THOUGHT EXPERIMENT (QUOTE P. 219)

IF ONE WERE SMALL ENOUGH TO PASS INTO SOMEONE’S BRAIN, ONE WOULD FIND NO PHYSICAL MECHANISM PRODUCING THOUGHT OR PERCEPTION.

THERE IS NO DOUBT THAT THINKING AND PERCEIVING ARE MYSTERIOUS

PHYSICS, CHEMISTRY AND BIOLOGY HAVE OFFERED NO PLAUSIBLE EXPLANATION OF THE EXISTENCE OR NATURE OF THOUGHT AND PERCEPTION. EVOLUTION DOES NOT SEEM TO HELP EXPLAIN THE DEVELOPMENT OF CONSCIOUSNESS AND RATIONAL THOUGHT. IF THE BRAIN PRODUCES THE RIGHT BEHAVIOR, SURVIVAL IS ENHANCED – BUT THERE IS NO APPARENT NEED FOR CONSCIOUSNESS.

BUT DOES LEIBNIZ’S THOUGHT EXPERIMENT FAVOR DUALISM?

VAN INWAGEN ARGUES THAT, ALTHOUGH THOUGHT AND PERCEPTION ARE MYSTERIOUS, DUALISM HAS NO ADVANTAGE IN ATTEMPTS TO EXPLAIN HOW SUCH THINGS OCCUR.SUPPOSE THAT THESE THINGS ARE CAUSED BY A NON-PHYSICAL THING. IS IT COMPOSITE? IS IT SIMPLE? ARE YOU ABLE TO IMAGINE HOW IT MIGHT PRODUCE THOUGHT AND ALLOW FOR PERCEPTUAL EXPERIENCE?

THE “OUTSIDER” WOULD SEE CERTAIN PHYSICAL THINGS GOING ON THE BRAIN

• THE “INSIDER”, THE ONE WHOSE BRAIN IS PRODUCING THOUGHT OR EXPERIENCE, WOULD HAVE OR EXPERIENCE THESE THINGS

DIFFERENTLY.• BUT COULDN’T THE PHYSICAL EVENTS JUST BE

THE VERY SAME EVENTS AS THE “MENTAL” EVENTS?

“WHERE” ARE THE MENTAL EVENTS OCCURRING?

IN SO FAR AS EVENTS HAVE LOCATION, THE MENTAL EVENTS ARE OCCURRING IN THE VERY SAME PLACE AS THE PHYSICAL BRAIN EVENTS – THEY ARE THE PHYSICAL BRAIN EVENTS (ACCORDING TO THE PHYSICALIST)

VAN INWAGEN CONCLUDES THAT THE LEIBNIZIAN ARGUMENT FAILS

THE THOUGHT EXPERIMENT BRINGS OUT HOW STRANGE MENTAL EVENTS ARE (EXPERIENCED FROM THE “INSIDE”), BUT IT DOES NOT SHOW THAT PHYSICAL THINGS CANNOT HAVE THOUGHTS OR EXPERIENCE.

G. E. MOORE

A THIRD ARGUMENT THAT A PERSON IS NOT A BODY

• G. E. MOORE’S OBSERVATION ABOUT “WHERE” HE IS.

(1) I AM CLOSER TO MY HANDS THAN I AM TO MY FEET.

(2) MY BODY IS NOT CLOSER TO MY HANDS THAN TO MY FEET.THEREFORE (BY DD):(3) I AM NOT MY BODY.