Blog Archives

An Argument based on Maydole’s Interpretation of Proslogion 2

Robert Maydole uses definite descriptions and Russell’s theory of descriptions to explicate Anselm’s first ontological argument in Proslogion 2.  I like the idea of using definite descriptions in the argument, and broadly agree with Maydole that Anselm intends to treat “that than which none greater can be conceived” as a definite description.  I do have some issues with Maydole’s formulation, however.  1) I think of Anselm’s argument as a reductio, but that isn’t how Maydole formulates it, 2) there are extra premises in Maydole’s formulation that are ultimately unnecessary, in my opinion, e.g. his seventh premise below 3) there is a typological error’s in Maydole’s argument, which is a minor quibble, but this seems to be a common problem with Maydole’s arguments in the Blackwell Companion to Natural Theology. It doesn’t appear that the editors proofed his arguments very well, to be honest. This is not to say that Maydole’s arguments are not ingenuiously formulated.

Maydole’s argument is formulated as follows:

Ux ≝ x is understood
Sy ≝ the concept of y exists-in-the-understanding
Ex ≝ x exists-in-reality
Gxy ≝ x is greater than y
Fxy ≝ x refers to y
Dx ≝ x is a definite description
d ≝ the definite description “(ɿx) ~©(∃y)Gyx”
g ≝ (ɿx)~©(∃y)Gyx
P(Y) ≝ Y is a great-making property
©… ≝ it is conceivable that…

Here then is our logical reconstruction of Anselm’s ontological argument:

A1 The defi nite description “that than which it is not conceivable for something to be greater” is understood. (Premise)

A2 “That than which it is not conceivable for something to be greater” refers to that than which it is not conceivable for something to be greater. (Premise)

A3 The concept of whatever a defi nite description that is understood refers to has existence-in-the-understanding. (Premise)

A4 It is conceivable that something is greater than anything that lacks a great-making property that it conceivably has. (Premise)

A5 Existence-in-reality is a great making property. (Premise)

A6 Anything the concept of which has existence-in-the-understanding conceivably has existence-in-reality. (Premise)

A7 It is not conceivable that something is greater than that than which it is not conceivable for something to be greater. (Premise)

Therefore,

A8 That than which it is not conceivable for something to be greater exists-in-reality.

The following deduction proves that this argument is valid:

Deduction

1. Dd & Ud pr
2. Fdg pr
3. (x)(y)((Dx & Fxy & Ux) ⊃ Sy) pr
4. (x1)(Y)[(P(Y) & ~Yx1 & ©Yx1) ⊃ ©(∃x2)Gx2x1] pr
5. P(E) pr
6. (x)(Sx ⊃ ©Ex) pr
7. ~©(∃y)Gyg pr
8. Fdg & ~©(∃y)Gyg 2, 7 Conj
9. (∃x)[~©(∃y)Gyx & (z)(~©(∃y)Gyx ⊃ z=x) & (Fdx & ~©(∃y)Gyx)] 8, theory of descriptions1
10. ~©(∃y)Gyν & (z)(~©(∃y)Gyz ⊃ z=ν) & (Fdν & ~©(∃y)Gyν) 9, EI
11. ~©(∃y)Gyν 10, Simp
12. Fdν 10, Simp
13. (P(E) & ~Eν & ©Eν) ⊃ ©(∃x2)Gx2ν 4 UI
14. (Dd & Fdν & Ud) ⊃ Sν 3 UI
15. (Dd & Fdν & Ud) 1, 12, Simp, Conj
16. Sν 14, 15 MP
17. Sν ⊃ ©Eν 6, UI
18. ©Eν 16, 17 MP
19. ~(P(E) & ~Eν & ©Eν) 13, 11 MT
20. ~((P(E) & ©Eν) & ~Eν) 19 Com, Assoc
21. ~(P(E) & ©Eν) ∨ ~~Eν) 20, DeM
22. P(E) & ©Eν 5, 18 Conj
23. Eν 21, 22, DS, DN
24. ~©(∃y)Gyν & (z)(~©(∃y)Gyx) ⊃ z=ν) 10 Simp
25. ~©(∃y)Gyν & (z)(~©(∃y)Gyx) ⊃ z=ν) & Eν 23, 24 Conj
26. (∃x)[~©(∃y)Gyx & (z)(~©(∃y)Gyx) ⊃ z=x) & Ex] 25 EG
27. Eg 26, theory of descriptions
(Maydole 2012, 555-557).

My version is adapted from Maydole and runs this way:

P1. Possibly, God, the x such that there is not some y such that y conceivably has greater capacities, exists in the understanding.

P2. For all x, if possibly x exists in the understanding, it is conceivable that x exists in reality.

P3. For all x, if it is not the case that x exists in reality, and x can exist in the understanding such that it is conceivable that x exists in reality, then there is some y such that y is the proposition “x exists in reality” and there is some z such that y refers to z, z can exist in the understanding and z conceivably has greater capacities than x.

C1. The x such that there is not some y such that y conceivably has greater capacities than x, i.e. God, exists in reality.

The formal deduction is as follows, let:

Cx ≝ it is conceivable that x exists in reality
Ix ≝ x exists in intellectu
Rx ≝ x exists in re
Fxy ≝ x refers to y
Gxy ≝ x conceivably has greater capacities than y
g ≝ (ɿx)~(∃y)Gyx

1. ♢Ig (premise)
2. (∀x)[♢Ix ⊃ Cx] (premise)
3. (∀x){[~Rx & (♢Ix &Cx)] ⊃ (∃y)[(y = ⌜Rx⌝) & (∃z)((Fyz &♢Iz) & Gzx)]} (premise)
4.♢Ig ⊃ Cg(2 UI)
5.♢Ig ⊃ (♢Ig & Cg) (4 Exp)
6.♢Ig & Cg (1,5 MP)
7. ~Rg (IP)
8. ~Rg & (♢Ig & Cg) (6,7 Conj)
9. [~Rg & (♢Ig & Cg)] ⊃ (∃y)[(y = ⌜Rg⌝) & (∃z)((Fyz & ♢Iz) & Gzg)](3 UI)
10. (∃y)[(y = ⌜Rg⌝) & (∃z)((Fyz & ♢Iz) &Gzg)] (8,9 MP)
11. (μ = ⌜Rg⌝) & (∃z)((Fμz & ♢Iz) & Gzg) (10 EI)
12. (Fμν &♢Iν) & Gνg (11 EI)
13. Gνg (12 Simp)
14. (∃y)Gyg (13 EG)
15. (∃x){[~(∃y)Gyx & (∀z)(~(∃y)Gyz ⊃ (z = x))] & (∃y)Gyx} (14 theory of descriptions)
16. [~(∃y)Gyμ & (∀z)(~(∃y)Gyz ⊃ (z =μ))] & (∃y)Gyμ (15 EI)
17. ~(∃y)Gyμ & (∀z)(~(∃y)Gyz ⊃ (z =μ)) (16 Simp)
18. ~(∃y)Gyμ (17 Simp)
19. (∃y)Gyμ (16 Simp)
20. (∃y)Gyμ & ~(∃y)Gyμ (18,19 Conj)
21. ~~Rg (7-20 IP)
22. Rg (21 DN)

QED

1This line has an error and should be: (∃x)[~©(∃y)Gyx & (z)(~©(∃y)Gyz ⊃ z=x) & (Fdx & ~©(∃y)Gyx)

Reference:
Maydole R. 2012. “The Ontological Argument”. In The Blackwell Companion to Natural Theology. Ed. W.L. Craig & J.P. Moreland. Malden, MA: Blackwell Publishing, pp. 555-557.

Advertisements

The Modesty of Maydole’s Temporal Contingency Argument

In a recent discussion that I had, my interlocutor claimed that “contingency” was an outdated scholastic concept. Really it is just a modal property. Sometimes it is called “two-way” possibility, i.e. x is contingent iff possibly and possibly not x. Temporal contingency the possibility of existing at some point in time and not existing at some point in time. We experience temporal contingency all the time. Anyways, I promised to explain how contingency is still relevant today in the philosophy of religion. In fact, I think it is relevant in one of the most powerful arguments for God’s existence. I can’t really imagine a good reason to deny any of the premises, and it is of course logically valid. So I am compelled to conclude that it is a sound argument for the existence of a supreme being, which I call “God”.

In a sense, The argument originates with Thomas Aquinas’s third way, but is developed by Robert Maydole, who fuses it with a modal ontological argument to devise an ingenious new argument.

Maydole defines a supreme being as follows:

D1. A supreme being is such that it is not possible that there exists anything greater than it and it is not possible that it is not greater than anything else that is non-identical to it.

He then proves the following, which we will call T1:

T1. If possibly a supreme being exists, then a supreme being exists.

Maydole does this by making use of a few theorems, like Barcan Formula, and other theorems in modal logic (I will reproduce the argument below, for those who are interested, see the conditional proof on lines 4-19 for the exact proof). Then Maydole constructs an argument for the possibility of a supreme being. He lists the following premises (but don’t attack them straight off, something interesting happens):

P1. Something presently exists.
P2. Only a finitely many things have existed to date.
P3. Every temporally contingent being begins to exist at some time and ceases to exist at some time.
P4. Everything that begins to exist at some time and ceases to exist at some time exists for a finite period of time.
P5. If everything exists only for a finite period of time, and there have been only a finitely many things to date, then there was a time when nothing existed.
P6. If there was a time when nothing existed, then nothing presently exists.
P7. A being is temporally necessary if and only if it is not temporally contingent.
P8. Everything has a sufficient reason for its existence.
P9. Anything that has a sufficient reason for its existence also has a sufficient reason for its existence that is a sufficient reason for its own existence.
P10. No temporally contingent being is a sufficient reason for its own existence.
P11. Every temporally necessary being that is a sufficient reason for its own existence is a being without limitations.
P12. A being without any limitations is necessarily greater than any other being.
P13. It is not possible for anything to be greater than itself.
P14. It is necessarily the case that “greater than” is asymmetric.

From P1-P14 one can prove C1:

C1. A supreme being exists.

The proof from P1-P14 to C1 is a bit long, and I believe Maydole even made a few typographical mistakes along the way. Here is my adaptation of this part of the argument, if you are interested.

Next consider what was said, before, that if it is possible that a supreme being exists, then a supreme being exists, i.e. T1. Maydole’s argument is surprisingly modest. What he does is argue that POSSIBLY (P1-P14) is true. Since C1 is provable from (P1-P14), we can say POSSIBLY C1 is true, which is to say that possibly a supreme being exists. Given T1 and the possibility that a supreme being exists, we can conclude that a supreme being exists (which is rightly called God)!

Now, the argument is very strong, because it is plausible that P1-P14 are actually true. However, Maydole only requires that the premises be possibly true rather than actually true, which is to say that they are not logically or metaphysically incoherent, or that they are true in some metaphysically possible world (as contemporary modal logicians would say). The deduction is valid, and it is very hard for me to think any of the premises are false. So I am compelled to think that this is, indeed, a sound argument for God’s existence.
So the proof looks something like this:

Let

Gxy ≝ x is greater than y
Sx ≝ (~◊(∃y)Gyx & ~◊(∃y)(x≠y & ~Gxy))

1. ◊(P1-P14) (premise)
2. (P1-P14) ⊢ C1 (premise that C1 is provable from P1-P14)
3. {◊(P1-P14) & [(P1-P14) ⊢ C1]} ⊃ ◊C1 (premise)
4. ◊(∃x)Sx (Assump CP)
5. ◊(∃x)Sx ⊃ (∃x)◊Sx (BF theorem)
6. (∃x)◊Sx (4,5 MP)
7. ◊Su (6 EI)
8. ◊(~◊(∃y)Gyu & ~◊(∃y)(u≠y & ~Guy)) (7, df “Sx”)
9. ◊(~◊(∃y)Gyu & ~◊(∃y)(u≠y & ~Guy)) ⊃ (◊~◊(∃y)Gyu & ◊~◊(∃y)(u≠y & ~Guy)) (theorem)
10. ◊~◊(∃y)Gyu & ◊~◊(∃y)(u≠y & ~Guy) (8,9 MP)
11. ◊~◊(∃y)Gyu (10 Simp)
12. ◊~◊(∃y)(u≠y & ~Guy) (10 Simp)
13. ◊~◊(∃y)Gyu ⊃ ~◊(∃y)Gyu (theorem, by “S5”)
14. ◊~◊(∃y)(u≠y & ~Guy) ⊃ ~◊(∃y)(u≠y & ~Guy) (theorem, by “S5”)
15. ~◊(∃y)Gyu (11,13 MP)
16. ~◊(∃y)(u≠y & ~Guy) (12,14 MP)
17. ~◊(∃y)Gyu & ~◊(∃y)(u≠y & ~Guy) (15,16 Conj)
18. Su (17, df “Sx”)
19. (∃x)Sx (18 EG)
20. ◊(∃x)Sx ⊃ (∃x)Sx (4-19 CP, which proves T1)
21. {◊(P1-P14) & [(P1-P14) ⊢ C1] (1,2 Conj)
22. ◊C1 (3,22 MP)
23. ◊(∃x)Sx (22, def “C1”)
24. (∃x)Sx (20,23 MP)

QED

To me, it is P11 that needs more explanation. It certainly seems right that a temporally necessary being who is the sufficient reason for its own existence has the sort of existence that is not limited by time nor by the existence of any other thing. But to say that the existence of x is not limited by time nor any thing seems a bit different from saying thag such a being is essentially without limitations. I believe the idea is that if there is no time nor state of affairs in which such a being would cease to exist or lack a reason for existing, then it is not limited by anything at all, and must be greater than every other thing.

Another person noted that P5 did not make sense to him because time is something that exists, so there could never be a time when nothing exists. Maydole, however, is quantifying over things in a way that is distinct from moments (in his “Modal Third Way” you see a more careful distinction between moments and things). With the right qualifications, and stipulations, this worry can be alleviated, e.g. one might say “no concrete things” or “no subsitent things” rather than “nothing”.

Reference:
Maydole, R. 2012. “The Ontological Argument”. In The Blackwell Companion to Natural Theology. Ed. W.L. Craig & J.P. Moreland. Malden, MA: Blackwell Publishing, pp. 580-586.

Plantinga’s Ontological Argument


Things have been pretty crazy lately and so I have been forced to slow my posting while I try to meet some deadlines. However, I thought I would start a series on the Ontological Argument as it is of interest to me.

Here is Plantinga’s version of the argument as laid out by R.E. Maydole (The Blackwell Companion to Natural Theology 2009, 590):

Let
Ax =df x is maximally great
Bx =df x is maximally excellent
W(Y) =df Y is a universal property
Ox =df x is omniscient, omnipotent, and morally perfect

Deduction:

1. ◊(∃x)Ax                                      pr                           
2. □(x)(Ax ≡ □Bx)                               pr
3. □(x)(Bx ⊃ Ox)                                pr
4. (Y)[W(Y)≡(□(∃x)Yx ∨(□~(∃x)Yx)]              pr
5. (Y)[∃(Z)□(x)(Yx ≡ □Zx)⊃ W(Y)]               pr
6. (∃Z)□(x)(Ax ≡ □Zx)                          2,EG
7. [(∃Z)□(x)(Ax ≡ □Zx) ⊃ W(A)]                5,UI
8. W(A)≡(□(∃x)Ax ∨(□~(∃x)Ax)                 4,UI
9. W(A)                                         6,7 MP
10. W(A)⊃(□(∃x)Ax) ∨ (□~(∃x)Ax)               8,Equiv, Simp
11*. □(∃x)Ax ∨ □~(∃x)Ax                     9,10 MP
12. ~◊~~(∃x)Ax ∨ □(∃x)Ax                     11,Com, ME
13. ◊(∃x)Ax ⊃ □(∃x)Ax                         DN, Impl
14. □(∃x)Ax                                    1,13 MP
15. □(x)(Ax ≡ □Bx) ⊃ (□(∃x)Ax ⊃ □(∃x)□Bx)    theorem
16. □(∃x)□Bx                                   14,15 MP (twice)
17. □(x)(Bx ⊃ Ox) ⊃ (□(∃x)□Bx ⊃ □(∃x)□Ox)    theorem
18. □(∃x)□Ox                                   16,17 MP (twice)
19. (∃x)□Ox                                    18,NE

*Premise 11 seemed to contain an error. I added the disjunctive symbol as it was missing from Maydole’s account.

So, the argument is valid. The question is with the premises. Most take issue with premise 1, that it is possible that there exists something that is maximally great. One response that I have heard is that while the burden of proof is on the person making the positive assertion, in the cases of probability, the benefit of the doubt sides with the person supposing possibilities. In other words, one must provide me with good reasons to suppose some proposition could not obtain in any possible world. How would one do this in this case? Any thoughts?

%d bloggers like this: