Why would a person have free will just becuase someone else has foreknowledge of the choice they will make?

The problem with this is that for Anselm, God is an absolute presupposition. That means he does not "prove" anything about God; his "proof" is merely a demonstration for "the fool." Gaunilo called him on it, and Anselm (apparently) said he didn't care, meaning if nothing else he (Anselm) understood his own argument perfectly.

as the characteristics required of a maximally great being cannot coexist in one being, thus such a being could not exist. — Yajur

Characteristics cannot exist in one being? Why not?

I think he meant the specific characteristics he mentioned, the 3 “O”’s as it were.
I would take it a step further and suggest the traits themselves are nonsensical,

Anything Walt Whitman could do, God can do.

Why would a person have free will just becuase someone else has foreknowledge of the choice they will make? — DingoJones

Free will is the power of acting without the constraints of necessity or fate.
If God has foreknowledge of a persons choice, then the person is constrained to that choice.
Hence rendering him without free will.

Anything Walt Whitman could do, God can do. — tim wood

If Walt could become an atheist, can God become an atheist too?

The foreknowledge of what the person will choose doesn't effect the choice the person will make, unless the person with foreknowledge tells the person but even then not in every case.
Let me demonstrate:
You have a choice between your worst possible scenario or your best possible scenario.
I know which one you will choose, does that mean you no longer have a choice? Certainly not, you still have very good reasons for choosing your best possible scenario and very good reasons to not choose your worst possible scenario. Fate has nothing to do with it, foreknowledge of something isnt fate. It is simply an awareness of the factors that will lead to a certain decision.

I vote for Aquinas's argument against Anselm - that we do not posses the ability or the tools to, in anyway, accurately imagine the nature of God.

aside - I think the Ontological argument is elegant logic, and not a very good proof of the existence of God.

Anything Walt Whitman could do, God can do.
— tim wood

If Walt could become an atheist, can God become an atheist too? — Yajur

Nice! I suppose we could assay just exactly what "atheist" means - that might answer. But I'll try a different answer: given a sufficiently broad definition/understanding of "God," I argue that it is impossible to be an a-theist. What definition/understanding would that be? Simply a belief that there is an account of the world. Under that definition, to be an atheist would be to deny that there is any such account(ing) of the world.

If instead you wish to limit atheism to the denial of the existence of certain beings, you're free to do so, but I consider both sides of that argument too trivial to waste time on.

I know which one you will choose, does that mean you no longer have a choice?

-DingoJones

It is an interesting situation that you bring up. Is it true that having foreknowledge of what the person will choose does not affect the choice the person will make? I believe that in the case of God, His foreknowledge could certainly affect the choice that one makes. I had trouble discerning what your premises to your argument might be. However, I have produced a counter-argument that may better explain my argument:

1. If you have free will to choose, then you must have the possibility to choose each of those options
2. If an omniscient God knows what you will choose, you would not have the possibility to choose anything else.
3. Therefore, if God knows what you will choose, you would not have the free will to choose (MT 1,2)

Similar to your argument, I assumed that the omnipotent God knows what you will choose. I will expand upon premise 2 as I believe that it is the most difficult part of my argument to conceptualize. To simplify the situation, let's say that you had an option between choice A and choice B. Let us also say that an omniscient God knew that you were going to choose A. When faced with these decisions, suppose you chose A. This would be perfectly fine as it is in line with what God knew you would choose. However, let’s say that you choose B. Choosing B would mean that God did not actually “know” that you were going to choose A. This seems obvious as you did not end up choosing A, so God must have been mistaken in “knowing” that you were going to choose A. In this case, God did not truly know that you were going to choose A (because you chose B instead), meaning that He is not truly omniscient. Therefore, in the cases where God is truly omniscient, choice B is not a possible choice, as God could not possibly be omniscient while incorrectly judging that you would choose A.
This would suggest that in this situation, option B is not really a possibility and that there is only the illusion that you could choose between A and B, while in reality, A is the only “choice” that could be chosen. This means that God’s omniscience really does pose an issue for free will and the ability to choose in the face of foreknowledge.

1. If you have free will to choose, then you must have the possibility to choose each of those options
2. If an omnipotent God knows what you will choose, you would not have the possibility to choose anything else.
3. Therefore, if God knows what you will choose, you would not have the free will to choose (MT 1,2) — Abecedarian

2 simply restates the position my argument is meant to dispel. It still does not follow that gods foreknowledge effects the decision the person is making. You just sort of added another layer and then draw the same conclusion.
You go into greater detail but I think you make a mistake here:

“However, let’s say that you choose B.”

If you choose B, then that would have been the foreknowledge the omniscience granted, not that A would be chosen. You’ve made a logical loop de loop here.
Lets say you are the kind of person who, all things considered equal, seeks to preserve his life rather that end it. Lets say you are given a binary choice between being executed by a firing squad or having a nice meal. I am not omniscient but I know which one you are going to choose. Obviously, the meal. Does that mean you have no choice but to choose the meal? I dont think it does. You have good reasons not to go with the firing squad, and so you do. My foreknowledge doesnt effect your decision, the factors of the choice do.
The only way foreknowledge effects your choice is if You were to be to informed of the foreknowledge, and that would be incorporated into your choice now, though you are still very likely to make the same choice in the example above. If you became aware of what you were going to do, then you might make a different decision, which would be harder for me to predict. Omniscience would get it right though and as the factors of the choice change, so would the foreknowledge.
You cannot bait and switch an omniscient being, their knowledge/foreknowledge adjusts to any changes you make to the equation. This is because the omniscient being has perfect knowledge of the factors of the choice, not because the being has precognitive powers. An important distinction.

I believe there is a tension between knowledge of the future (entailed by omniscience) and the notion of omniscience. I'd describe it thusly:future, freely willed acts are unknowable:

t0: 1AM, Jan 1 1920
t1: 1AM Jan 1, 2020

P1: Jack drinks a glass of beer at t1 (the chosen act is a product of libertarian free will)
P0: God has knowledge of P1 on at t0.
(de re semantics stipulated throughout)

There is no truthmaker of P1 at t0, so how can this constitute knowledge at t0?
(where truthmaker: = an elements of reality to which the proposition corresponds)

(note the difference between a freely willed act and one that is the product of determination)

1.) Iff God made Jack choose to drink the beer at t1, then choice of action action would be a product of determination.
2.) God’s omnipotence gives Him power to look at the future.
3.) Jack chooses to drink the beer at t1.
4.) God has knowledge that Jack chose to drink the beer at t1, at t0.
5.) Jack acted upon his free will at t1 and God has knowledge of what his choice will be at t0 without intervening in any way.
6.) Jack’s beer drinking at t1 is not a product of determinism.

In this situation we are not tied to saying that God forced Jack to drink the beer, showing that a future, freely willed act is possible. Jack can choose to drink the beer at t1 and God can have knowledge of this act at t0.

Your assertion, "2.) God’s omnipotence gives Him power to look at the future."
Is defeated by my argument. God can't do the logically impossible.

I am treating A-theory of time (presentism) as true.

Your assertion, "2.) God’s omnipotence gives Him power to look at the future."
Is defeated by my argument. God can't do the logically impossible.

I am treating A-theory of time (presentism) as true. — Relativist

Relativist, while God and time may belong on a different forum, I think an understanding of how God can understand the future in A-theory of time pertains to the debate about the Ontological argument by defending @princessofdarkness situation in which God knows the future, but does not determine it. It seems that your objection goes something like this:
1. At a time (t0), a future time (t1) only exists as a series of potentialities
2. A series of potentialities has no truth making capabilities, therefore nothing can be known with epistemological certainty
3. God cannot know what happens at t1 at time t0
4. God cannot be all-knowing (1,3 MP)
Even in an A-theory of time, certainly some propositions exist at that present moment, and God knows the truth of all those propositions at that current moment. So if someone were to say, "Jack is going to drink a beer at t1" God knows the truth of that proposition, and so knows what will happen at t1. It does not seem that A-theory directly eliminates the possibility of God's foreknowledge.

To connect this with the ontological argument, it seems that princessofdarkness's case holds up, and the God can be both omnipotent and omniscient, even in A-theory of time.

Or you could be a B-theorist :)

"Even in an A-theory of time, certainly some propositions exist at that present moment, and God knows the truth of all those propositions at that current moment. So if someone were to say, "Jack is going to drink a beer at t1" God knows the truth of that proposition, and so knows what will happen at t1. It does not seem that A-theory directly eliminates the possibility of God's foreknowledge"
You are asserting God knows, not showing how it can be possible. It is impossible because libertarian free will implies Jack's actions aren't determined. Drinking a beer is only a possibility at t0.

You are asserting God knows, not showing how it can be possible — Relativist

My apologies, I assumed God's omniscience was true definitionally true based on the ontological argument, and that you were merely questioning how can omniscience and free will can go together. I fail to see how you have challenged the ontological arguments premises besides rejecting its conclusion? If the ontological argument is to be taken as true, it seems that the conclusion of an omniscient God is true, and so we can then assume based on the reasoning above that there is not a problem with omniscience and foreknowledge, which I believe was at the heart of your post:

I believe there is a tension between knowledge of the future (entailed by omniscience) and the notion of omniscience. I'd describe it thusly:future, freely willed acts are unknowable: — Relativist

As you noted, I was highlighting the tension. At least one of the following seems likely to be false:
God is omniscient (where omniscient entails knowledge of the future)
Libertarian free will exists
A-theory of time is true
Brute facts don't exist

Omniscience could be revised to mean only that God knows everything that is knowable. This would imply he can only know elements of the future that are the product of strict determinism.

Perhaps brute facts exist (God knows the future by brute fact) but this undermines some important reasons to believe a God exists (i.e. the Leibniz' Cosmological Argument).

Perhaps compatibilism is true, and therefore determinism is true, although this undermines a common theist response to the problem of evil.

Perhaps B-theory is true.

or perhaps we have no capacity to understand what God is at all. And all of our anthropomorphic rationalizations and theories are akin to an ant trying to understand astrophysics.

That's a fine attitude to couple with faith. On the other hand, arguments for God's existence depend on conceptual analysis, so words like "omniscience" have to to be taken to mean something.

and while the ant may have an ant definition of astrophysics, it may have nothing at all to do with astrophysics. However the ants can still enjoy arguing about it, and even asign one ant or another the title of smartest ant.

Some ants debate the existence of God. A theist ant can't expect to persuade an atheist ant by mere assertion and handwaving. The converse is also true, so perhaps we can just agree that God is a hypothetical possibility.

Not really about Anselm's ontological argument...

I guess, in this case, omniscience is not so much about causation as it's about truth.

1. suppose, for the sake of argument, that here in 2018 I know exactly how 2020 will unfold
2. knowledge implies truth, cannot be false, non-negotiable
3. come 2020, my foreknowledge can then not fail to occur, regardless of whatever else, everything must then occur as foreknown
4. everyone's goings and doings, my own included, are not free to diverge in any way, even if I had told everyone what would occur, since then my foreknowledge would be false
5. absence of freedom is seemingly contrary to free choice, including my own, throughout 2020

No particular dependence on causation, only on truth, as per the foreknowledge.

Some ants debate the existence of God. A theist ant can't expect to persuade an atheist ant by mere assertion and handwaving. The converse is also true, so perhaps we can just agree that God is a hypothetical possibility. — Relativist

Theists don't normally - or classically use the 3 O's in their proofs of God. These are beliefs theists hold by faith, and are outside reason. For example - the CA 's only conclusion is there was, at least at one time, an un-created creator, that is all. The entire basis of the OA is that God is outside our ability to imagine, and in the arguments from design, only one of the O's is implicit.

It is way more common for atheists to describe this theist belief that is held by faith, as a basis of an argument and then defeat one of the O's with reason. They establish a proposition that has never been offered as derived by reason - then say it is not reasonable. This is the basis of the the argument from evil and all the O paradoxes. And the theist response to both at the end of the day is the same - we have no idea at all with the limited tools we posses, any true definition of what God is.

Irrespective of whether you consider this normal, I've encountered numerous theists who present Alvin Plantinga's ontological argument as proof of God's existence. Plantinga's argument utilizes this premise:

Necessarily, a being has maximal excellence in every world only if it has omniscience, omnipotence, and moral perfection in every world

I also think he does acknowledged in his argument that the God of 3 O's is outside reason - from memory could well be mistaken

If so, that sounds self-defeating.

from Wikipedia - use with caution - My take is this is just applying Modal logic to Anselm's base argument. Instead of saying what we can imagine, it is just saying - something is possible - God of 3 O's in this is simply a restatement of " greatest being that can be imagined in Anselm argument.

1. A being has maximal excellence in a given possible world W if and only if it is omnipotent, omniscient and wholly good in W; and

2. A being has maximal greatness if it has maximal excellence in every possible world.

It is possible that there is a being that has maximal greatness. (Premise)

Therefore, possibly, it is necessarily true that an omniscient, omnipotent, and perfectly good being exists
.
Therefore, (by modal logic axiom S5) it is necessarily true that an omniscient, omnipotent and perfectly good being exists.

Therefore, an omniscient, omnipotent and perfectly good being exists.

Plantinga argued that, although the first premise is not rationally established, it is not contrary to reason.

finally as an aside - while i enjoy the logic in both, i think neither is a very effective proof of God -

Thanks for the reference. It seems to me that the premise could be considered contrary to reason if the omniscience is incoherent or unintelligible.

Personally - I have no real position on the reasonableness of the 3O's one way or the other. As a skeptical theist - i don't believe we have any ability at all, in any meaningful way, to say anything at all about the nature of God. It is why I do not believe either the OA or the intelligent design arguments are effective.