Descartes' second proof of God's existence in the Meditations

@kennethamy,

kennethamy wrote:

Yes. We should try to decide whether the argument is a sound argument. But that cannot be decided by a show of hands. I don't know who the "king" is supposed to be. St. Anselm first in invented the argument in the 13th century, and Descartes revived it in the 17th century. Are they the "kings"? Most philosophers believe that ontological argument has been refuted. But not by a show of hands. (In fact, even in Descartes's time, several criticisms were offered. The criticisms of the logic were never, "I am not convinced", since that is not a relevant criticism of the argument).

Criticism is the debate ,does it go on forever and ever.In three pages i have seen opinions expressed that it was wrong and certain reasons why but i never saw a valid reason why.Is that criticism or a conviction?When is conviction not a criticism? when one stops replying?

@xris,

xris wrote:

Criticism is the debate ,does it go on forever and ever.In three pages i have seen opinions expressed that it was wrong and certain reasons why but i never saw a valid reason why.Is that criticism or a conviction?When is conviction not a criticism? when one stops replying?

The reason the ontological argument goes wrong is that is assumes that existence is a property, and that is false. Existence is not a property. That is the standard refutation of the argument.

Failure of conviction is not a criticism of the logic of the argument. It may, of course, be a criticism of the utility of the argument. But that is different. Good arguments may fail to convince, just as bad arguments (fallacies) may succeed in convincing. And, just as success does not mean the argument is a good argument, so failure does not mean the argument is a bad argument.

@kennethamy,

kennethamy wrote:

The reason the ontological argument goes wrong is that is assumes that existence is a property, and that is false. Existence is not a property. That is the standard refutation of the argument.

Failure of conviction is not a criticism of the logic of the argument. It may, of course, be a criticism of the utility of the argument. But that is different. Good arguments may fail to convince, just as bad arguments (fallacies) may succeed in convincing. And, just as success does not mean the argument is a good argument, so failure does not mean the argument is a bad argument.

How do you decide what argument is deserving of discussion.Is it because it is of philosophical historic interest? or can it stand on its own?Do we join the melee because of who prescribed the logic or is it valued for its own sake? A sixteenth century thinker has a perspective on faith that can be astounding in its determination,can we argue against that view from our place in history.

@xris,

xris wrote:

How do you decide what argument is deserving of discussion.Is it because it is of philosophical historic interest? or can it stand on its own?Do we join the melee because of who prescribed the logic or is it valued for its own sake? A sixteenth century thinker has a perspective on faith that can be astounding in its determination,can we argue against that view from our place in history.

I would suppose that if the argument interests you, and if you find it important, then why should it not be worthy of discussion? Of course, you may be alone in your assessment, and then it is open to you to argue, and try to convince others of the interest and importance of the argument. People have found the ontological argument interesting and important since it was invented by a fairly obscure monk, St. Anselm. It was, they felt, an intriguing argument, not least because some felt that there must be something wrong with it, for it seemed to "define" God into existence. But it was really not until first Hume, and then, Kant, that the flaw in the argument was pinpointed. That existence is not, as Kant wrote, "a predicate". The history of what has been called, "the many-faced argument" is very interesting. But it really has nothing much to do with the logical soundness of the argument.

@Bones-O,

One may have an idea of something: that idea is to know various properties of it. My idea of a triangle comes from knowing the properties of a triangle. However, in a reasonable argument, an idea should be defined else we do not know what the proof is proving. So Descartes defines his idea by stating some of its properties: infinite, perfect, existing. If an idea cannot contain the thing's existence, then I am no more sure that unicorns don't exist, or that the Lord Nelson monument does exist. One could say that the existence is associated to, but not in, the idea, but then just expand the idea to include it. This is, to be sure, inconsistent with Descartes' method, since he doubts what he sees and so cannot acquire clear and distinct ideas he doesn't already hold, at least in this stage of the argument. But taking the argument out of context, I don't see the problem in defining an idea partly by specifying its existence, since the idea of a non-existent thing is radically altered when we find it exists, and vice versa (or was your idea of Santa Claus unaltered by his non-existence*).

This is the freedom of defining something to be discussed in an argument. If we define God to exist, and the argument holds, and God doesn't exist, we may reject the definition. Since God is an empirically non-falsifiable entity by design, we need to look at the argument to see whether or not the definition is appropriate for the argument. As it happens, the only part of the definition of the idea of God pertaining to the proof of his existence is the property of existence (the circular argument, if the idea is held). Thus anything defined to exist exists, including unicorns and a triangle whose angles add up to more than or less than 180 degs. That's taking the proof on its own merits, without respect to the first, or any other argument, i.e. to take 'the essence of God contains the existence of God' as an assumption that may be rejected, rather than as proven fact than cannot. In the latter case, we come to some version of the first proof which can be rejected on other grounds and also gives us grounds to reject the second proof due to circularity of argument again (God exists rather than is defined to exist, therefore God exists).

The point of this thread was to check if the above counter-argument is valid, taking the second proof out of any context. i.e. I'm looking for criticism of my above argument, not on refutations of Descartes' second proof in general (as per my OP). Any assistance gratefully received.

*With apologies to those who didn't know.

@Bones-O,

Bones-O! wrote:

One may have an idea of something: that idea is to know various properties of it. My idea of a triangle comes from knowing the properties of a triangle. However, in a reasonable argument, an idea should be defined else we do not know what the proof is proving. So Descartes defines his idea by stating some of its properties: infinite, perfect, existing. If an idea cannot contain the thing's existence, then I am no more sure that unicorns don't exist, or that the Lord Nelson monument does exist. One could say that the existence is associated to, but not in, the idea, but then just expand the idea to include it. This is, to be sure, inconsistent with Descartes' method, since he doubts what he sees and so cannot acquire clear and distinct ideas he doesn't already hold, at least in this stage of the argument. But taking the argument out of context, I don't see the problem in defining an idea partly by specifying its existence, since the idea of a non-existent thing is radically altered when we find it exists, and vice versa (or was your idea of Santa Claus unaltered by his non-existence*).

This is the freedom of defining something to be discussed in an argument. If we define God to exist, and the argument holds, and God doesn't exist, we may reject the definition. Since God is an empirically non-falsifiable entity by design, we need to look at the argument to see whether or not the definition is appropriate for the argument. As it happens, the only part of the definition of the idea of God pertaining to the proof of his existence is the property of existence (the circular argument, if the idea is held). Thus anything defined to exist exists, including unicorns and a triangle whose angles add up to more than or less than 180 degs. That's taking the proof on its own merits, without respect to the first, or any other argument, i.e. to take 'the essence of God contains the existence of God' as an assumption that may be rejected, rather than as proven fact than cannot. In the latter case, we come to some version of the first proof which can be rejected on other grounds and also gives us grounds to reject the second proof due to circularity of argument again (God exists rather than is defined to exist, therefore God exists).

The point of this thread was to check if the above counter-argument is valid, taking the second proof out of any context. i.e. I'm looking for criticism of my above argument, not on refutations of Descartes' second proof in general (as per my OP). Any assistance gratefully received.

*With apologies to those who didn't know.

The problem is whether it makes sense to define anything as existing. What does it mean to say of X that X exists (or does not exist)? If I say that X does not exist, am I contradicting myself. For instance, if I say that mermaids do not exist (which I suppose we all believe is true) can I be contradicting myself? If it is part of the definition of God that He exists, then, if I say, that God does not exist, then I must be saying something that is self-contradictory. Is that really possible? Yet that is what the ontological argument implies. Consider what Hume wrote in this connection. He wrote, "Whatever exists might not exist".

@kennethamy,

kennethamy wrote:

The problem is whether it makes sense to define anything as existing. What does it mean to say of X that X exists (or does not exist)? If I say that X does not exist, am I contradicting myself.

As per my post you quoted, I may define a triangle to have more or less than 180 degs: this is the freedom associated with defining something for consideration. That a triangle always has exactly 180 degs (as can be shown) is grounds for dismissing that definition. To this extend, as much as a definition may be accepted or rejected, there is no problem with defining something to exist. You seem to think we have to avoid contradiction in a proof: many proofs rely on contradiction. If we can show that 'God is defined as existing' leads to a contradiction, which we cannot, we can reject that definition and make progress.

kennethamy wrote:

For instance, if I say that mermaids do not exist (which I suppose we all believe is true) can I be contradicting myself?

Unless you define mermaids as something that exist, no.

kennethamy wrote:

If it is part of the definition of God that He exists, then, if I say, that God does not exist, then I must be saying something that is self-contradictory. Is that really possible?

Yes. Here's another example: a triangle is defined as having three sides. A square is a triangle with four sides. I have contradicted myself, so I must address this either by changing the definition of the triangle or the square.

---------- Post added at 12:45 PM ---------- Previous post was at 12:38 PM ----------

kennethamy wrote:

The problem is whether it makes sense to define anything as existing.

I am happy to admit there are other problems with Descartes' proof, and that this may be one of them. But this particular problem is not the thread topic. I'm happy to open this up to other topics relating to the proof, but I'm a little gutted that I can't get anyone to post on-topic at all, esp. as this is my first thread ever! It's not going well, I don't know why... :perplexed:

Can I persuade you to let the problem you cite lie for a post or two and look at other problems? Namely:

(i) Anything whose essence is to exist is shown to exist by Med V;
(ii) Non-existence is consistent with incorrect definition (not God --> no idea).

@Bones-O,

Bones-O! wrote:

As per my post you quoted, I may define a triangle to have more or less than 180 degs: this is the freedom associated with defining something for consideration. That a triangle always has exactly 180 degs (as can be shown) is grounds for dismissing that definition. To this extend, as much as a definition may be accepted or rejected, there is no problem with defining something to exist. You seem to think we have to avoid contradiction in a proof: many proofs rely on contradiction. If we can show that 'God is defined as existing' leads to a contradiction, which we cannot, we can reject that definition and make progress.

Unless you define mermaids as something that exist, no.

Yes. Here's another example: a triangle is defined as having three sides. A square is a triangle with four sides. I have contradicted myself, so I must address this either by changing the definition of the triangle or the square.

---------- Post added at 12:45 PM ---------- Previous post was at 12:38 PM ----------

I am happy to admit there are other problems with Descartes' proof, and that this may be one of them. But this particular problem is not the thread topic. I'm happy to open this up to other topics relating to the proof, but I'm a little gutted that I can't get anyone to post on-topic at all, esp. as this is my first thread ever! It's not going well, I don't know why... :perplexed:

Can I persuade you to let the problem you cite lie for a post or two and look at other problems? Namely:

(i) Anything whose essence is to exist is shown to exist by Med V;
(ii) Non-existence is consistent with incorrect definition (not God --> no idea).

But can't i have an idea of God as an omnipotent, omniscient, etc. Being, and yet question whether anything with those properties exists? After all, as Kant pointed out, my idea of God as existing is no different from my idea of God as not existing. Just as my idea of a unicorn as existing is no different from my idea of a unicorn as not existing. Unless you can tell me how idea of the unicorn that doesn't exist differs from the idea of a unicorn that does exists. Or, the idea of a God that does exist differs from the idea of one that does not exist. What has the one idea, that the other idea does not have?

The point is that there can be nothing whose essence is to exist. And that is because an essence is a property of something, But existence is not a property of anything, and therefore, there is nothing whose essence is existence.

Non-existence is not inconsistent with the definition of God because no definition (of God, or anything else) can include existence. To say that X exists is to say that the definition of X applies to something. It is not to say that the definition of X includes existence. So, you are asking that two clearly false propositions be assumed as being true. Yes, if we assume that existence is a property, and that existence is part of the definition of God (which amounts to the same thing) then if would follow that God must exist. But both of those assumptions are false.

@kennethamy,

kennethamy wrote:

I would suppose that if the argument interests you, and if you find it important, then why should it not be worthy of discussion? Of course, you may be alone in your assessment, and then it is open to you to argue, and try to convince others of the interest and importance of the argument. People have found the ontological argument interesting and important since it was invented by a fairly obscure monk, St. Anselm. It was, they felt, an intriguing argument, not least because some felt that there must be something wrong with it, for it seemed to "define" God into existence. But it was really not until first Hume, and then, Kant, that the flaw in the argument was pinpointed. That existence is not, as Kant wrote, "a predicate". The history of what has been called, "the many-faced argument" is very interesting. But it really has nothing much to do with the logical soundness of the argument.

Im really confused here we have an argument on logic but the soundness of the logic is not being questioned? What is being questioned the result of this logic or the logic that came to this result?

@xris,

xris wrote:

Im really confused here we have an argument on logic but the soundness of the logic is not being questioned? What is being questioned the result of this logic or the logic that came to this result?

You think that every time we criticize an argument, we have first to discuss what you call, "the soundness of logic"? Suppose that someone argues that since all dogs are mammals, that all mammals are dogs. And I say, it doesn't follow that because all dogs are mammal, all mammals are dogs. And he replies, that I am only questioning the result of the argument, and I am not questioning logic itself. You think that is a proper point to make?

Why not do the same thing in other fields. Suppose I point out that since the refrigerator is not working, and the temperature is higher than freezing, that if you put water into an ice-tray and expect it to form ice, you will be disappointed. Should you say that I am not questioning physics, but only the result of the physics?

@kennethamy,

kennethamy wrote:

You think that every time we criticize an argument, we have first to discuss what you call, "the soundness of logic"? Suppose that someone argues that since all dogs are mammals, that all mammals are dogs. And I say, it doesn't follow that because all dogs are mammal, all mammals are dogs. And he replies, that I am only questioning the result of the argument, and I am not questioning logic itself. You think that is a proper point to make?

Why not do the same thing in other fields. Suppose I point out that since the refrigerator is not working, and the temperature is higher than freezing, that if you put water into an ice-tray and expect it to form ice, you will be disappointed. Should you say that I am not questioning physics, but only the result of the physics?

Sorry i dont understand how the logic being used is not the same as the proposal being questioned.His logic is saying one thing and the outcome is from his logic.Now Ive questioned the logic and Ive questioned the outcome and you say we should not be doing either, but how he arrived at his conclusion.I then question how we can question the mind of believer and that was wrong, sorry but this debate is turning into a semantic enquiry.

@kennethamy,

kennethamy wrote:

The problem is whether it makes sense to define anything as existing. What does it mean to say of X that X exists (or does not exist)? If I say that X does not exist, am I contradicting myself. For instance, if I say that mermaids do not exist (which I suppose we all believe is true) can I be contradicting myself? If it is part of the definition of God that He exists, then, if I say, that God does not exist, then I must be saying something that is self-contradictory. Is that really possible? Yet that is what the ontological argument implies. Consider what Hume wrote in this connection. He wrote, "Whatever exists might not exist".

Again, a problem is whether it makes sense to define anything as existing. Descartes clearly thinks it does. Hume's and Kant's refutations are reasonable and justifiable, however they are not relevant to the question I've asked. I will clarify and again ask that you at least pay some lip service to the question posed in the OP: Irrespective of whether a thing may be defined as existing, Descartes' second proof does not hold on grounds of (i) circularity of argument; (ii) non-uniqueness of outcome; (iii) the contradiction of the conclusion only leads to the contradiction of what Descartes claims to know, i.e. not only may the definition be unfeasible (an issue not pertaining to this thread) but it is also not applicable (which does pertain to this thread) even if it were feasible.

@Bones-O,

Bones-O! wrote:

Again, a problem is whether it makes sense to define anything as existing. Descartes clearly thinks it does. Hume's and Kant's refutations are reasonable and justifiable, however they are not relevant to the question I've asked. I will clarify and again ask that you at least pay some lip service to the question posed in the OP: Irrespective of whether a thing may be defined as existing, Descartes' second proof does not hold on grounds of (i) circularity of argument; (ii) non-uniqueness of outcome; (iii) the contradiction of the conclusion only leads to the contradiction of what Descartes claims to know, i.e. not only may the definition be unfeasible (an issue not pertaining to this thread) but it is also not applicable (which does pertain to this thread) even if it were feasible.

I have to admit that I do not understand your objections. What, for instance is circular about the argument?
Descartes does not think he is "defining" God into existence. He does not think it has anything to do with the meaning of the word, "God". Descartes believes he is not defining a word at all. What he thinks is that he is discovering the real meaning of God. It is as if he were a kind of scientist and he discovered that the element, gold, had certain necessary properties like:
Atomic number 79
Atomic mass
196.9655 g.mol -1
Electronegativity ccording to Pauling
2.4
DensityMelting pointBoiling point

None of the above has anything to do with the word, "gold". It has to so with substance, gold. It is what Descartes would have called (in medieval language, a "real definition". A definition of the thing, not the word. Only the thing here is, "God". Just as it is an essential property of gold that its atomic number is 79, so, it is the essential property of God that he exists. A "real definition" By the way is contrasted with a "nominal definition". A definition of the word, not the thing.

Perhaps you find this a weird way of thinking, but that is how Descartes thought about it.

@kennethamy,

Thanks Ken.

kennethamy wrote:

None of the above has anything to do with the word, "gold". It has to so with substance, gold. It is what Descartes would have called (in medieval language, a "real definition". A definition of the thing, not the word. Only the thing here is, "God". Just as it is an essential property of gold that its atomic number is 79, so, it is the essential property of God that he exists. A "real definition" By the way is contrasted with a "nominal definition". A definition of the word, not the thing.

Sure, I didn't mean anything to the contrary. Now let's see how that works out...

It is an essential property of the thing gold that it has atomic number 79.
Therefore the thing gold has atomic number 79.

Still looks pretty circular to me. I can follow how the argument constitutes a statement of a discovery that existence is a necessary property of God, but that is not how it is presented. It is presented as proof (insofar as it ends "and therefore God surely exists"), and yet just as it being essential that gold have A=79 does not prove gold has A=79, it being essential God exists does not prove God exists. It is the proof, after all, that I'm interested in.

By way of another contrast, it is sufficient to show: "I think, therefore I exist". Descartes does not say, "I think, therefore I must exist. I must exist, therefore I exist" since the second statement tells us nothing, just as "God must exist, therefore God exists" tells us nothing.

@Bones-O,

Bones-O! wrote:

Thanks Ken.

Sure, I didn't mean anything to the contrary. Now let's see how that works out...

It is an essential property of the thing gold that it has atomic number 79.
Therefore the thing gold has atomic number 79.

Still looks pretty circular to me. I can follow how the argument constitutes a statement of a discovery that existence is a necessary property of God, but that is not how it is presented. It is presented as proof (insofar as it ends "and therefore God surely exists"), and yet just as it being essential that gold have A=79 does not prove gold has A=79, it being essential God exists does not prove God exists. It is the proof, after all, that I'm interested in.

.

I guess I don't understand just what you think is circular. Of course, if an essential property of gold is that its atomic number is 79, then it follows that one of its properties is, atomic number, 79. Just as if being a mammal is an essential property of being a dog, then being a mammal is a property of being a dog. After all, all essential properties are also, properties. What is circular about that?

And, if existence is an essential property of God's, then existence is a property of God's. So, God exists. And, since to say that p is an essential property of X, is to say that X necessarily is p, to say that existence is an essential property of God's is to say that God necessarily exists (God not only does exist, but must exist; it is impossible for God not to exist). I don't see why any of this is circular. Of course, again, if it is an essential property of God's that he exist, and since all essential properties are properties, then God has the property of existence, and that means the same as, God exists (just as if apples have the property of being red, that means the same as, apples are red. And, if gold has the property of its atomic number being 79, that is the same as saying that gold has the atomic number, 79. So I don't see your objection.

As I have been saying, the issue is whether existence can be a property of anything at all, including God.

Of course, Descartes does not say, I think, therefore I must exist. If he did, he would be God. He would be saying that he necessarily existed! What he does say is that, it must be, that if I think I (do) exist. And that is different.

@kennethamy,

kennethamy wrote:

I guess I don't understand just what you think is circular. Of course, if an essential property of gold is that its atomic number is 79, then it follows that one of its properties is, atomic number, 79. Just as if being a mammal is an essential property of being a dog, then being a mammal is a property of being a dog. After all, all essential properties are also, properties. What is circular about that?

But, again, you confuse description with proof. Gold having the essential property of A=79 is not proof gold has A=79. The proof that gold has A=79 relies on other observations, such as mass-to-charge ratio and ionisation energies. From these, we deduce gold has A=79.

Whereas, in Med V, Descartes' proof that God exists is that God's essence is that he exists. As a description, fine, but not as an argument, for it is circular, just as 'It is an essential property of dogs to be mammalian, therefore dogs are mammals' is circular: the conclusion is the premise.

kennethamy wrote:

Of course, Descartes does not say, I think, therefore I must exist. If he did, he would be God. He would be saying that he necessarily existed! What he does say is that, it must be, that if I think I (do) exist. And that is different.

And yet one must exist in order to think. "I think, therefore I could exist" allows "I don't exist" which contradicts "I think", therefore I must exist - my existence is a necessary condition of the world and this is demonstrated, however that God's existence is a necessary condition of the world is the premise of the argument. God's existence is not deduced from this, since it is in the premise itself. In your reasoning, Descartes actually derives a weaker statement (God exists) from a stronger one (God must exist), which again is proof of nothing.

@Bones-O,

Bones-O! wrote:

But, again, you confuse description with proof. Gold having the essential property of A=79 is not proof gold has A=79. The proof that gold has A=79 relies on other observations, such as mass-to-charge ratio and ionisation energies. From these, we deduce gold has A=79.

Whereas, in Med V, Descartes' proof that God exists is that God's essence is that he exists. As a description, fine, but not as an argument, for it is circular, just as 'It is an essential property of dogs to be mammalian, therefore dogs are mammals' is circular: the conclusion is the premise.

And yet one must exist in order to think. "I think, therefore I could exist" allows "I don't exist" which contradicts "I think", therefore I must exist - my existence is a necessary condition of the world and this is demonstrated, however that God's existence is a necessary condition of the world is the premise of the argument. God's existence is not deduced from this, since it is in the premise itself. In your reasoning, Descartes actually derives a weaker statement (God exists) from a stronger one (God must exist), which again is proof of nothing.

If gold'sl atomic number is 79, then gold has the essential property of having atomic number, 79.
And, if gold has the essential property of having atomic number 70, then gold has the property of having atomic number, 79.
Therefore, if gold's atomic number is 79, then gold has the property of having atomic number, 79.

So that is a proof that gold has the property of having atomic number, 79.

Let me add, that, of course, to know that all the premises are true, and so, to know that the first premise is true, we have to make observations. I cannot know the premises are true, (as philosophers say) a priori, (independently of observation). So the proof I gave relies, of course, on the truth of the premises of the argument, and the premises of the argument rely, for whether or not they are known to be true, on observation (broadly speaking). But, that does not mean that the above argument is not an argument to show that atomic number 79 is not a perfectly valid argument for its conclusion. It is. And if the premises are also true, then we have a sound argument for the conclusion, and that means that the conclusion is true. But there is no circularity. The argument is perfectly valid, and the conclusion follows necessarily from its premises. So, (in a parallel way) to argue that since the essential property of God is existence, it follows that existence is a property of God (just as to argue that since it is a color property of apples that apples are red, it follows that red is a property of apples.) And, in general, is follow from the premise that x is a y/property of z, that x is a property of z's. Just as, to give one more example, it follows from the fact that John is my brother, that John is a brother.

I don't see that the argujment, I exist, therefore I could think, contradicts, I exist. After all, I could think allows for I don't think, but it does not actually state, or even imply, I don't think. But anyway, that X does not think, does not contradict, X exists. Chairs don't think, but chairs exist. If I think, then I exist, is logically independent of, if I exist, then I think. Neither statement implies the other, nor does the falsity of either statement imply the other.

I don't think you can possibly mean that you must exist. You know very well that there was a (long) time when you did not exist, and (alas) a probably even longer time when you won'y exist. So how is it possible that you must exist? In fact, I think it is false that anything must exist, since if it were true of anything that it must exist, then existence would be a property of that thing. But since existence is not a property of anything (at all), existence cannot be a property of that thing. Nothing must exist, but some things (indeed, everything) does exist.

But you are on to something when you say that the statement that God must exist, derives from the statement that God does exist, in the ontological argument. Indeed, the philosopher, Leibniz wrote that it is a "privilege" reserved only to God, that not only did the very fact of His existence proved that He must exist, but that even the very possibilty of His existence, was sufficient for His existence. Why? Because, if God is a possible being, then His existence is an essential property of Him, and if an essential property, then, of course, a property. So if God is even a possible being, God is a necessary being. If it is even possible that God should exist, it is impossible that God should not exist. For that is what it means to say that existence is an essential property of God's. Therefore, Leibniz argued that the ontological proof was incomplete. It was necessary to show that it was possible for God to exist. That is, that the concept of God does not imply a contradiction (like the concept of square-circle). But once we do that; once we show that the concept of God is not impossible, is the concept of a possible being, then, Leibniz argued, we are home free, for it would then follow that God is an actual being. And Leibniz then proceeded to try to give a proof that God is a possible being. And, he thought he did so.

@kennethamy,

Hi Ken. Thanks again.

kennethamy wrote:

If gold'sl atomic number is 79, then gold has the essential property of having atomic number, 79.
And, if gold has the essential property of having atomic number 70, then gold has the property of having atomic number, 79.
Therefore, if gold's atomic number is 79, then gold has the property of having atomic number, 79.

So that is a proof that gold has the property of having atomic number, 79.

This is fine, but no longer analogous to Descartes' proof insofar as we ascertain that gold has A=79, then from the above arguments deduce it must do so. Descates starts from the premise that God must exist, then 'deduces' God exists. This is not a proof as far as I can see. For one thing, the conclusion is uniquely defined in a single premise, not deduced from it.

I understand your point now that the argument isn't circular: many thanks, this is precisely what I was after. If X must exist, then X exists. However if X exists it doesn't hold that X must exist: it may be contingent on other factors. That said, the nature of God and his relationship with existence does seem to rule out any such contingent factors - if we consider this then the argument does become circular again.

Nonetheless, I was basing my criticism on an incorrect interpretation of the word 'necessary'.

It does make me wonder if there is a counter-argument here as well. If it is necessary that X exists, does it follow X exists or simply that X should exist?

kennethamy wrote:

Just as, to give one more example, it follows from the fact that John is my brother, that John is a brother.

Yes, this is what I found unproof-like in Descartes' proof. We cannot draw that John is a brother from John being my brother since John being my brother depends on John being a brother. Being a brother is a necessary though not sufficient condition of John being my brother. Again, the conclusion is contained uniquely within the premise. Such an argument proves nothing, though if you say this is perfectly acceptable within philosophy, I will accept this too. (I'm not a philosopher, but a physicist. One of the reasons I stayed away from philosophy for so long was that texts I had read did not match up to the rigour I had gotten used to in physics. This point I've been stuck on may be hangover from my different background's methods of reasoning. 'X must be therefore X is' is difficult for me to accept, but I will.)

kennethamy wrote:

I don't see that the argujment, I exist, therefore I could think, contradicts, I exist. After all, I could think allows for I don't think, but it does not actually state, or even imply, I don't think. But anyway, that X does not think, does not contradict, X exists. Chairs don't think, but chairs exist. If I think, then I exist, is logically independent of, if I exist, then I think. Neither statement implies the other, nor does the falsity of either statement imply the other.

I'm not sure how this follows what I've said. I did not say 'I exist,therefore I think'. I said 'I think, therefore I necessarily exist', though I now agree this is wrong.

kennethamy wrote:

But you are on to something when you say that the statement that God must exist, derives from the statement that God does exist, in the ontological argument.

Hang on, how can you agree that 'God must exist' depends on 'God exists' then deny any circularity in stating "God must exist, therefore he exists", since by your own admission this is equivilent to saying "God exists (plus some other stuff), therefore God exists" and since the conclusion does not depend on the other stuff, we can simplify it as "God exists, therefore God exists", which is a circular argument.

kennethamy wrote:

So if God is even a possible being, God is a necessary being. If it is even possible that God should exist, it is impossible that God should not exist. For that is what it means to say that existence is an essential property of God's. Therefore, Leibniz argued that the ontological proof was incomplete. It was necessary to show that it was possible for God to exist. That is, that the concept of God does not imply a contradiction (like the concept of square-circle). But once we do that; once we show that the concept of God is not impossible, is the concept of a possible being, then, Leibniz argued, we are home free, for it would then follow that God is an actual being. And Leibniz then proceeded to try to give a proof that God is a possible being. And, he thought he did so.

Thanks for that. Very interesting. I'll have to check out Leibniz's version of the proof, though from what I've read of the Monadology, Leibniz's reasoning around God seems to lose credibility in the same way Descartes' does in the Meditations. Still... one thing at a time.

Cheers Ken. Very helpful and enlightening stuff.

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Descartes' second proof of God's existence in the Meditations

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