"They're suppose to" works perfectly fine regardless of determinism. And this is only one of many, many reasons people might have for praying. All of which makes your attempts to shoehorn "selfishness" into this conversation for hundreds of posts, and this remains terrible even if you had a lock solid argument that praying is provably a logical contradiction.

If you can't change god's mind, why would you be supposed to try to change god's mind?

because , under the determinism model, it can be claimed that they were pre-determined to pray

I've already explained this. First, the Bible isn't clear that god doesn't change his mind. Insofar as that is true, there is no mystery here at all.

Second, it is entirely conceivable that God has set up a system where his actions are contingent on our prayer. If so, he isn't "changing his mind" when he does x because we prayed. Under this kind of system whether or not God does x depends on whether we pray, even though God isn't changing his mind about whether or not to do x.

This shouldn't be that confusing (and also doesn't assume determinism). For example, suppose you made a rule for your daughter that you will only help her with her homework if she asks you for help. Suppose you somehow know that she will ask you for help (maybe you overhear her talking to a friend). So, you know you will help her with her homework, but yet your helping her is still contingent on her asking you for help. Notice that this doesn't assume determinism--her asking you for help can be a libertarian free-willed action and the story still makes sense. Notice also that you aren't changing your mind to help her when she asks you for help--it is just that you have earlier set up a rule that you will only help her if she asks, so if she doesn't ask then you won't help her and you are still following that rule.

Yes you have but I still have two issues with this. First that bible is inconsistent and contradictory and I don't regard it as a reliable source of knowledge about god. And secondly, that it doesn't seem logical that god's mind could be changed unless he isn't omniscient and I don't think that Christians would agree with that condition. Pre-determinism precludes changing god's mind, and as you say, what you suggest below is not changing god's mind, it's causing actions to occur that god has allowed for.

Thank you, I understand this. So it seems that in this scenario, someone seeking to change anything through praying to god, can at best hope that god has allowed for an action contingent on that prayer being made. What they can't do is stop anything that god has already decided to allow to happen, or vice versa.

This creates some intriguing possibilities and raises some difficult questions. Suppose person A prays for event X, but that can only actually occur if a million other events have previously occurred that could only occur if people prayed for them to happen, and somewhere in that chain of events, someone didn't make the required pray. Now person A doesn't get what they wanted, no matter that they prayed for it, and it's not because of god, they were in fact let down by someone who failed to make the appropriate prayer at the right time. What responsibilities does this place on us? Should we all pray for everything that could possibly occur, including things that are in conflict with each other, in case god has planned for it to happen or in case someone further down the line relies on us having done that? What if what we pray for prevents something another person's prayer from causing an event, is there then a responsibility to not pray to prevent that happening? What if you get what you prayed for but that sets in motion a chain of events leading to an unwelcome outcome for one or more people?

What if people pray for conflicting things, is god's choice of what will actually occur arbitrary?

First, I reject everything they believe.

Second, I insert my own theological framework in place of theirs, and then argue that their theology is wrong.

I would say: why not? The universe God created is largely arbitrary, why shouldn't his decisions be arbitrary as well?

Plus it keep the punters guessing.

What you are trying to do is show that intercessory prayer is inconsistent with the general theology of Christians. Since the claim that the Bible is inconsistent and contradictory (at least, significantly so) is not part of the general theology of Christians (even if it is true), this claim is irrelevant. So stop using using it. Every time you do I am forced to think that one of us doesn't understand your argument.

I could just as easily, and pointlessly, say that there is no god and that Jesus wasn't his Son, so intercessory prayer is not pointless. You are going for an inconsistency claim here, stick with it.

Just so we're clear, are you withdrawing your claim that intercessory prayer is inconsistent with the assumption of an omniscient, never-changing God?

Beyond that, I think most Christians would say that we should look to the Bible and/or Church tradition for lessons on how and for what we should be praying. Not for nothing, but Jesus does give directions on how to pray in his most famous sermon.