Ontological arguments for the existence of God

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St. Anselm (1033–1109)

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St. Anselm’s Proslogion

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The basic assumptions of Anselm’s argument

A crucial definition...

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A crucial distinction...

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A crucial principle...

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A crucial strategy...

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Anselm’s version of the ontological argument

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The target of Anselm’s reductio is the proposition that “God exists in the understanding alone”.

And since this assumption leads to an absurdity (that we can conceive of a being greater than the greatest conceivable being) our initial assumption must be false.

So, God exists both in the understanding and in reality

Is Anselm’s ontological argument convincing?

Evaluating Anselm’s ontological argument

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“I remember the precise moment, one day in 1894, as I was walking along Trinity Lane at Cambridge University, when I saw in a flash that the ontological argument is valid. I had gone out to buy a tin of tobacco; on my way back, I suddenly threw it up in the air and exclaimed as I caught it: ‘Great scott... the ontological argument is sound!’...”

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“It is much easier to feel convinced that the Ontological argument must be fallacious than it is to find out precisely where the fallacy lies...”

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So what’s wrong with Anselm’s argument exactly?

Is Anselm’s reasoning really on the right track?

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Guanilo of Marmoutier’s criticism of Anselm’s reasoning

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Guanilo’s lost island parody argument...

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What’s the point?

Guanilo of Marmoutier’s criticism of Anselm’s reasoning

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A possible Anselmian response to Guanilo...

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Immanuel Kant’s (1724–1804)objection to Anselm’s argument

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Immanuel Kant

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Is ‘existence’ really a predicate term?

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Is ‘existence’ really a predicate term?

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Another way to put the point of Kant’s criticism...

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Is premise (3) of Kant’s argument true? Is it true that saying of some X that ‘it exists’ adds nothing new?

Is ‘existence’ really a great making predicate?

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K:()6.(/0"#(,/()""4)(:%&)"(/0%/("9,)/"#2"(,)(%(-$"%/(4%+,#-(*$6*"$/'G(K#(?0,20(2%)".(>#)"&4A)(*$,#2,*&"(,)(@%7((

Does the ontological argument beg the question?

F64"(2$,12)(6:(/0"(6#/6&6-,2%&(%$-34"#/(0%8"(2&%,4"7(/0%/(>#)"&4A)(/0,#+,#-(2644,/)(/0"(:%&&%2'(6:('&*'+$(*)*-(0!"&"%

D0%/(,).(/0"(6#/6&6-,2%&(%$-34"#/()""4)(/6()64"06?(I)43--&"J(/0"(#616#(/0%/(!67("9,)/)(,#/6(/0"(*$"4,)")(6:(/0"(%$-34"#/(%#7(/0"#(;3#)3$*$,),#-&'<(7$%?)(/0"(26#2&3),6#(/0%/(!67("9,)/)G

Z#"(?%'(/6(/$'(/6(3#7"$)/%#7(/0,)(&,#"(6:(6@P"216#(,)(/6($"26#),7"$(>#)"&4A)(7"L#,16#(6:(!67(

All along, we’ve been treating “God is the (GCB)” as a a kind of definitional 1st

premise. But, isn’t this circular reasoning?

Maybe to avoid the circularity worry we would need to start out like this instead...

Is a non-circular version of the argument any good?

;R< W6$(%#'/0,#-(#!)'!+"#)(0(!67.(/0%/(/0,#-(?63&7(0%8"(/6(@"(/0"(;!CN<

@A+#B)"!5)#4(#)5->7-)'4("%-8).*-,&0-)@CDB)5-)($0!)4(7-)#!)(8E+0#)#4-)*-0#)!;)#4-)(*%+,-"#)(0)5-$$D

;S< D0"(;!CN<(*6))"))")("8"$'(*$6*"$/'(/0%/(?63&7(4%+"(%(@",#-(-$"%/

;T< ^9,)/"#2"(,)(%(*$6*"$/'(/0%/(?63&7(4%+"(%(@",#-(-$"%/

;U< W6$(%#'/0,#-(#!)'!+"#)(0(!67.(/0%/(/0,#-(?63&7(0%8"(/6(*6))"))("9,)/"#2"

;V< >#'/0,#-(/0%/(*6))"))("9,)/"#2"("9,)/)

D0"$":6$".

;_< >#'/0,#-(#4(#)'!+"#0)(0(!67(?63&7(0%8"(/6("9,)/

But now the conclusion stated in (6) is a bit underwhelming isn’t it?

Is there another version of the ontological argument that works?

A really simple version of the modal ontological argument

;R< K/(,)(.!00&6$-(/0%/(/0"(!$"%/")/(C6#2",8%@&"(N",#-("9,)/)

D0"$":6$".

;S< D0"(!$"%/")/(C6#2",8%@&"(N",#-("9,)/)

I/0.$&/">A#$1)$./%+8$"9$&>2/$0+$043>B)+.H$J&$%.$50A%#H$J&$%.$4)0&"+0'A)$."$')A%)5)$./)$*4&.$<0+#$"+A(@$C4)B%&)$"9$./)$043>B)+.H$$

Modal logic and possible worlds

A possible world is just a hypothetical way the world could have been

A really simple version of the modal ontological argument

;R< K/(,)(*6)),@&"(/0%/(/0"(;!CN<("9,)/)

D0"$":6$".

;S< D0"(;!CN<("9,)/)

I/0.$&/">A#$1)$./%+8$"9$&>2/$0+$043>B)+.H$

J&$%.$4)0&"+0'A)$."$')A%)5)$./)$*4&.$<0+#$"+A(@$C4)B%&)$"9$./)$043>B)+.H$$

Modal logic and possible worlds talk...

Y67%&(&6-,2(,)(/0"(&6-,2(6:(.!00&6&$&#:(%#7("-'-00&#:h*6)),@,&,/'(%#7(#"2")),/'(@",#-(/?6(I467")J(6:(/$3/0(%#7(:%&),/'.(/?6(?%')(,#(?0,20(%(*$6*6),16#(4,-0/(@"(/$3"(6$(:%&)"G

`6-,2(,#(-"#"$%&(/"&&)(3)(?0%/()6$/)(6:(,#:"$"#2")(%$"(-667(6#")(%#7(?0%/()6$/)(6:(,#:"$"#2")(%$"(@%7(6#")G(Y67%&(&6-,2(/"&&)(3)(%@63/(-667(%#7(@%7(,#:"$"#2")()*"2,L2%&&'(,#(/0"(764%,#(6:('$(&,0)(6!+#)54(#)&0).!00&6$-)("8)54(#)&0)"-'-00(*:

>(I*6)),@&"(?6$&7J(4,-0/(@"(/063-0/(6:(%)(%(264*$"0"#),8"(7")2$,*16#(6:(/0"(?%'(/0"(3#,8"$)"(,&%4#)6-

D0"(264*$"0"#),8"(7")2$,*16#(6:(63$(3#,8"$)"(,)(2%&&"7(/0"(('#+($)5!*$8G(N3/(#6/".(/0,#-)(4,-0/(0%8"(3#:6&7"7(7,]"$"#/&'(/0%#(/0"'(7,7(,#(/0"(%2/3%&(?6$&7

Modal logic and possible worlds talk...

>(I*6)),@&"(?6$&7J(4,-0/(@"(/063-0/(6:(%)(%(264*$"0"#),8"(7")2$,*16#(6:(/0"(?%'(/0"(3#,8"$)"(,&%4#)6-

D0"(264*$"0"#),8"(7")2$,*16#(6:(63$(3#,8"$)"(,)(2%&&"7(/0"(('#+($)5!*$8G(N3/(#6/".(/0,#-)(4,-0/(0%8"(3#:6&7"7(7,]"$"#/&'(/0%#(/0"'(7,7(,#(/0"(%2/3%&(?6$&7

W6$("9%4*&".(,/(263&7(0%8"(0%**"#"7(/0%/($%/0"$(/0%#(2066),#-(/6(*,2+(3*(/0,)(@66+(%#7($"%7(,/(/67%'.('63(2%&&"7('63$(:$,"#7)(%#7(?"#/(6#(%(0,+"(,#(/0"(463#/%,#)G(D0%/(7,7#A/(0%**"#.(6:(263$)"G(N3/(,/(263&7(0%8"G(D0"(7")2$,*16#(6:(/0"(?6$&7(,#(?0,20('63(7,7()6($"*$")"#/)(%#6/0"$(.!00&6$-)6+#)"!"?('#+($)5!*$8G(>)('63(2%#()"".(/0"$"(%$"(4%#'(*6)),@&"(?6$&7)h,#L#,/"&'(4%#'(,#(:%2/G(

Modal logic and possible worlds talk...

K#(7,]"$"#/(?6$&7).(7,]"$"#/(/$3/0)(06&7

W6$("9%4*&".(/0"(*$6*6),16#(I,$6#(%/64)("9,)/J(,)(/$3"(,#(/0"(%2/3%&(?6$&7.(@3/(,/(,)(:%&)"(,#(?6$&7)(,#(?0,20(/0"(3#,8"$)"("9*%#7"7(/66(e3,2+&'(:6$()/%$(:6$4%16#

F6(?0"#(?"(26#),7"$(%#'(*$6*6),16#.(?"(43)/(%))"))(,/)(/$3/0(6$(:%&),/'($"&%18"(/6(%(?6$&7G

i6/"(/0%/(?"(4,-0/.(,#(%77,16#(/6(/%&+,#-(%@63/(*$6*6),16#)(@",#-(/$3"(,#(%(?6$&7.(/%&+(%@63/(8%$,63)(#4&"%0)-<&0="%(;6$(#6/<((#(6$(&"(%(?6$&7G(O0"#()*"%+,#-(/0,)(?%'.(?"(2%#()%'(/0%/(,$6#(%/64)("9,)/(,#()64"(?6$&7).(%#7(#6/(,#(6/0"$)G

Modal logic and possible worlds talk...

K:()64"/0,#-(?"$"(/6("9,)/(,#("8"$'(*6)),@&"(?6$&7.(,/(?63&7("9,)/(#6(4%5"$(06?(/0,#-)(?"#/(6$(06?(/0"'(/3$#"7(63/a()320(%(@",#-(?63&7(@"(%("-'-00(*:)6-&"%

Z#(/0"(2&%)),2%&(26#2"*16#(6:(!67.(!67(,)(/%+"#(/6(@"(%(#"2"))%$'(@",#-

N",#-)(/0%/("9,)/(,#()64"(?6$&7)(@3/(#6/(,#("8"$'(?6$&7(%$"(2%&&"7('!"="%-"#)6-&"%0

Z#"(L#%&(26#2"*/(/0%/(26#),7"$"7(,)(/0"(26#2"*/(6:(.!00-00&"%).*!.-*=-0)"-'-00(*&$:(%#7('!"="%-"#$:G(O0"/0"$(%(@",#-(,)(#"2"))%$'(6$(26#1#-"#/.(/0"$"(%$"()64"(*$6*"$1")(/0%/(%(@",#-(?,&&(0%8"(,#("8"$'(?6$&7(,#(?0,20(,/("9,)/)

Axiom of S5 – If X is possible, then it is necessarily true that X is possible

A fuller version of the modal argument

;R< K/(,)(*6)),@&"(/0%/(!67("9,)/)

;S< K:(,/(,)(*6)),@&"(/0%/(!67("9,)/).(/0"#(!67("9,)/)(,#(%(*6)),@&"(?6$&7G

;T< K:(!67("9,)/)(,#(%(*6)),@&"(?6$&7.(/0"#(0"("9,)/)(,#(%&&(*6)),@&"(?6$&7)G

;U< K:(!67("9,)/)(,#(%&&(*6)),@&"(?6$&7).(/0"#(!67("9,)/)(,#(/0"(%2/3%&(?6$&7(;?0,20(,)(6#"(6:(/0"(4%#'(*6)),@&"(?6$&7)<G

D0"$":6$".

;V< !67("9,)/)(,#(/0"(%2/3%&(?6$&7G

D0"$":6$".(

;_< !67("9,)/)

If it’s possible for God to exist in one possible world, then it is necessarily true that God exists in all possible worlds

Is the modal ontological argument convincing?

Denying premise (1) and reversing the modal ontological argument...

;R< K/(,)("!#(*6)),@&"(/0%/(!67("9,)/)

;S< K:(,/(,)("!#(*6)),@&"(/0%/(!67("9,)/).(/0"#(!67(76")("!#("9,)/(,#(%(*6)),@&"(?6$&7

;T< K:(!67(76")("!#("9,)/(,#(%(*6)),@&"(?6$&7.(/0"#(0"(76")("!#("9,)/(,#(%#'(*6)),@&"(?6$&7)

;U< K:(!67(76")("!#("9,)/(,#(%#'(*6)),@&"(?6$&7).(/0"#(!67(76")("!#("9,)/(,#($"%&,/'

D0"$":6$".

;V< !67(76")("!#("9,)/(,#($"%&,/'G

D0"$":6$".(

;_< !67(76")("!#("9,)/

An interesting problem about the arguments to consider...

F,#2"(@6/0(/0"(*6),18"(%#7(#"-%18"(8"$),6#)(6:(/0"(467%&(%$-34"#/(%$"(8%&,7(,#(467%&(&6-,2.(%#7(/0"(26#2&3),6#)(%$"(26#/$%7,2/6$'.(/0%/(4"%#)(/0%/(/0"(.*-,&0-0(%$"(%&)6(26#/$%7,2/6$'(,#()64"()"#)"

F6(/0"(%&&(,4*6$/%#/(e3")16#()""4)(/6(@"(IO0,20(,#,1%&(*$"4,)"(76('63(0%8"(46$"($"%)6#(/*(@"&,"8"[(;%<(/0%/(,/(&0).!00&6$-(/0%/(!67("9,)/).(6$(;@<(/0%/(,/(,)("!#).!00&6$-(/0%/(!67("9,)/)XJ

O"()""4(/6(0%8"(%(Y"9,2%#()/%#7B6](6#(63$(0%#7)GGG

Is there any compelling reason to think that it’s impossible for God to exist?