FLEW'S FALSIFICATION PRINCIPLE: If you cannot show how X, say God, can be shown false then the idea of X, say God, is making no sense.  Its only an irrational assumption.

CRITIC: Basil Mitchell
Against Flew, Basil Mitchell said that Christians do admit that there are problems with belief in God which is why they describe evil as a problem. But if there is a God is it right or respectful to say that evil is a problem? Why not say, its a mystery like Job did in the Bible, and not a problem? Imagine you were a cashier who never makes mistakes and some customer claimed, "I believe in your perfect ability but I withdrew 100 dollars last week and only received 90 from you. I am not accusing you of making a mistake but this is a problem". Would you be impressed or convinced? Christians, no matter what they say, are saying there is a God and that evil refutes him and evil urges us to disrespect him if he does exist. He would then be unworthy of worship and respect. They are calling the refutation a problem but that doesn't make it a problem but a refutation.   
The talk about evil being a problem is the Christian trying to soften how evil disproves God. He is trying to hide it by gerrymandering with words.
Believers are only pretending to think of evil and suffering as a problem. Either way they are stubborn and put their God theory beyond falsification. That is cheating and dishonest and a proof in itself that no good God would want us to believe in him! Flew stands unrefuted. In fact, Mitchell is only showing that belief in God is more meaningless than Flew realised.
Mitchell said that Flew was wrong to say Christians put their God belief beyond any hope of falsification for they admit there are problems but he added that they refuse to doubt. They don't let the problems give them cause for doubt. The Christians are really just paying lip-service to the problems. If they really admitted the problems they would admit that the problems might disprove God and it would lessen their faith a bit. So Flew is right and Mitchell is wrong. The stubbornness of the Christian faith is a vice not a virtue. It is pure arrogance and insults reasonable people.
Mitchell thought that it is reasonable for believers to not let evidence against God harm their faith for they trust in God. They have reasons for thinking they can trust God. The girl may trust her boyfriend despite evidence that he is a shady character. But that would be okay if there is sufficient evidence that the evidence pointing to his guilt might be false or misleading. Mitchell is another one who expects you to trust God for nothing and remain reasonable.
Mitchell's reasoning seems to be that if you make a commitment to God it makes sense then afterwards to suspend judgement on any evidence that counts against belief in God. That is only true up to a point. Nobody should expect trust to go as far as saying a good God should let a baby suffer. It brings on the suspicion that the person is trying to feel better about the baby suffering. That would be a disgrace.
Mitchell thought that religious belief had some basis and was not entirely groundless. But what religious belief would that be? What if a religion worships demons and another one worships God? Mitchell pointed out that it is reasonable to trust an enemy who you have just met and who gives you a good impression despite the things they do later that look suspicious. He compared that to Christians getting a nice impression of God and letting it stay with them no matter what evil takes place. They keep believing and trusting. But that assumes that trust is always good or the best under the circumstances. Trying to trust a God when terrible things are happening could be more painful than just accepting or believing that there is nobody to trust
Mitchell talks nonsense. His nonsense only shows that Flew had to be right.
Ayer rejected falsification theory because nothing can be conclusively falsified at all for nothing can be absolutely verified either. No matter how good the evidence is for something there may be a tiny possibility that the conclusion it takes you to is wrong. The answer may be is that we are not talking about absolute proof for anything or absolute disproof but as much proof or disproof as we need.
The philosopher Hare decided that falsification theory could apply to statements of fact, eg Tony stole my wallet. But he said it could do nothing with existential statements such as the statement, God exists (page 355, OCR Philosophy of Religion for AS and A2). But statements of fact are saying that an act of stealing really existed and Tony existed and my wallet existed. Statements of fact and existential statements are inseparable. To say God exists is to make a statement of fact as well. You are saying God created Tony and gave him the power to steal. So God's role is a BIGGER statement of fact than Tony or his stealing. For the believer to say "Tony stole", translates as "God creates Tony and gave him the free will and power to steal and he stole because God creates him."
Many religious people do not claim that their beliefs and doctrines are based on knowledge. Cognitive refers to propositions that proceed from and are founded upon what is known to be true. Anything else is called non-cognitive. Hare believed that non-cognitive religious statements are meaningful.
If somebody thinks the Devil will destroy him unless he marries the nice girl he is going out with and is totally wrong and won't be influenced by any evidence that the Devil's threats are all in his head. This is said to have meaning if it motivates him to marry and make his life feel important. The man's belief is non-cognitive - it is not based on what he knows.
You don't perceive religion's teachings as facts but feel they make sense of your world then they are meaningful. They control the way you see the world. In other words, if belief in God is not based on facts or evidence, but helps you function as a sensible and rational person in your approach to life and the world, then the belief cannot be called meaningless. But it need not be a belief. It would still do this if it were a theory or even a fantasy.
Also, if you think belief in God gives reason and logic to your life and thinking that does not mean that the belief itself is logical or sensible. People think because they are used to their lives that they are controlling them. That is not a logical belief or sensible though it may help us be logical and sensible. In fact, why not just let ourselves feel we are in control? Why do we need to tell ourselves, "God is in control. I cannot change him. So the only way I can feel in control is if I agree to go along with him in everything"? That is unnecessary. It need not involve religion at all. It makes no sense to use religion for meaning because if you can use religion you are giving yourself the meaning so what do you need religion for? Why not just do it?
The notion that religion says non-cognitive things and that it gives you a way of looking at life and thus is making sense is mistaken. It does not really give you a way to make sense of life and your place in it. If religion could do that, the fact remains that this is irrelevant. It could be that a person who says their life gets meaning from their faith do not realise that faith does not play an essential role in it. There is more to living than religious faith. Nobody is content with God alone or they would be hermits. Life and the motivations that come with it is too complex for anybody to say that somebody's happiness or success is all down or principally down to their faith in religion or God.
It is easy for you to look at a religious person and say her faith is non-cognitive. What if she makes herself believe that it is? What if she is wrong? What if she thinks it is evidence-based or knowledge? If her faith is nonsense then she is clearly wrong to think her faith is knowledge. 
Believers usually talk and act as if their belief is cognitive. But is it? It is their actions alone that can tell the tale and they do. A person who thinks their beliefs are cognitive is more likely to try and force them on others. The more a person practices their faith and supports its doctrines the more the person is acting as if they have sound truth based reasons to believe. They are not acting like their faith is non-cognitive so they are cognitive. If so their religious beliefs are meaningless.
God by definition means the being who you should die for if required. A person who feels there is a God and claims to have no evidence and then sets about dying for God as a martyr or something is deranged. Do not encourage such by saying their faith is non-cognitive and valid and reasonable. If non-cognitive beliefs and faiths are okay then faith in God is still out.
CRITIC: Swinburne
Swinburne said that you cannot show that your toys come out and move around when nobody is around to see. He said we still understand what it means to say the toys come alive and come out. So for him, talking about toys coming to life and moving has meaning for us. But that is not what the principle is about. It is about the statement that the toys have done this. It is about fact and not the meaning of coming to life or moving. It is about whether it makes sense to call something that cannot be refuted a fact.
CRITIC: John Hick

He declared "Religious belief can be verified in principle if true, but never falsified if false".
He was talking about religion as he knew it. But it is obvious that some religions have to be falsified just as anything of human origin can be.
If Hick is right, why does religion make little effort to examine itself and its beliefs? It does not seem to care if it can be verified in principle or not. A religion getting it right does not mean that the religion is truly from God. What if it is right through luck rather than the truth? The problem of having an idol instead of God who looks like God is insurmountable.
Because of this the Falsification Principle can never be about making sense of God. It has to start off with the fact that God makes no sense.
Nobody has ever experienced spirit - you can only experience what feels like it but that is not the same as examining or testing spirit. A spirit is a being that is real but has no parts or material components so it cannot be tested or discovered or experienced. It cannot be distinguished from imagination. For many of us, spirit is purely imagined. God is spirit which means that if spirit is nonsense then God cannot exist. There is no way of showing if spirit is possible or impossible. Thus the Falsification Principle shows it is nonsense.
To claim that God exists is a bigger thing than saying a ghost lives in the cellar. God by definition is that which is entitled to extreme sacrifice of devotion. We should be willing to suffer to the extreme forever for him if he needed us to. Thus if God is meaningless and so is the ghost, God is extreme meaninglessness. The ghost though bad isn't so bad. Thus it is heinous to put God beyond refutation. It is too important to go that far with it.
If we need to be so arrogant and stubborn that nothing will falsify our belief in God then clearly God is a bad concept. It encourages badness. If you want a concept that does that and which encourages belief then you are saying that God is good though he encourages bad belief or belief that is a vice. That makes God meaningless for you are contradicting yourself. You can't have a chaste adulterer and so you cannot have a God that blesses vice. If the God concept comes from vice then why should we trust the religious deliberations of those who advocate it? Why should we pay any attention to alleged evidence for God?
The Nazis put Hitler's views and politics beyond criticism or any hope of being refuted. No matter what Hitler did or didn't do, it was right. Look what that led to. They did the warped good of being loyal to him. If the God belief encourages such loyalty, what if the loyalty is given to evil men like Hitler instead? Hitler got some good out of the loyalty. That was terrible but it is far worse to give such loyalty to a being you cannot even see like God! If you can put the God who empowered Hitler and kept him in existence beyond criticism then you have not far to go to start doing that with Hitler too.
Having reasons for belief means only that you are trying to be reasonable not that you are reasonable. All contrary or unreasonable people have reasons for what they say they believe or do. It is reality that is the final arbiter if you are really reasonable or not. Even those who use reason and are rationalists must admit that they strive towards reason in many things. You can have a million reasons for believing that St Thomas masqueraded as Jesus after Jesus was stolen from the tomb and that he was called the Twin for they were really twins but if Jesus rose from the dead your belief is against reason and that is final. Reason is trying to find what is real.
FP Definitely applies to God if nothing else
CS Lewis said that you cannot trust your senses if you didn't get them from an all-good and all-honest God. If God exists then he alone matters so knowledge only matters if he gives it to us. It is only then that it is possible. Now if God is only a guess, then it is against knowledge to say, "God gives us knowledge. If there is no God there is no knowledge. Those who think they know things are deluded." It is against knowledge for it bases knowledge on a guess. Knowledge is not knowledge if it is all about a guess. If you have to guess that we have knowledge, then guess it. Do not bring in props such as God. That is like trying to prop up a house of cards that is about to fall by making it fall harder. If falsification theory is useless as some hope, it works in the case of God. It ruins the God concept. It is dishonest to guess that there is a God and that is how you know things. Why not simply guess that you know things? God is simply too big of a claim for nonsense such as that! It makes nonsense of God too. And that is what the Falsification Principle does. It makes nonsense of God talk. God is the one thing that needs the Falsification Principle more than anything ever could. It is simple - if you think you know nothing you cannot mean anything you say so it is meaningless. If you try to base knowledge on God you will be unable to. It will not happen. You in fact make things worse and you are lying that you know things when you are only guessing.
Now if you need God before you can claim knowledge then what knowledge matters most? What knowledge should be sought if you have to choose? The answer would be spiritual and theological knowledge. If you are allowed different forms of knowledge that knowledge has to be based on spiritual or God knowledge.
Religion goes as far as to argue that the concept of good cannot exist unless you believe in God. But we treat good as real whether we believe in God or not. You don't need a God to convince you that eating healthy makes you well. Even if you think it is a sin to be well, you think it is good to be sick so you cannot get away from good. Religion keeps trying to get away from it to create an artificial good: God.

Think of God but not as a unit
Religion treats God, a being with different properties as a unit to try and dodge the scalpel that is the Falsification Principle. This is because the unit does not look as ridiculous and stops you considering each one of the forces that make up God and their individual significance.
What is the most important thing about God? What is the most important and basic thing he has? If we honour God and love him we will honour that the most.
Free will?
Power to create from nothing?
It would be power. There is no life without power. So life is next.
This is the correct order.
Knowledge - you need to know you are alive to have free will
Free will
Love - there is no love so we are told, unless free will is there
Power to create from nothing

So you get the order right.  Then you apply the principle to each one. 

If something is made untestable then if you are going to say x you must admit you can say a or b or c ad infinitum.  So it is meaningless.  You intend to be meaningless when you say it.  Words that would normally mean something are meaningless for you take meaning from them.

Custard is custard whether it is a spoonful or a lake.  Meaningless is meaningless. Yet the more important the thing you make untestable the more meaninglessness you state it with.


So to sum up God is a pile of untestable statements and the biggest statements about him quantity wise make the most meaninglessness.

Some merit
Suppose the Falsification Principle is wrong. If so then it is not totally bad. There is some merit in it. We might that say something that cannot be disproved is a little meaningless. The more an effort is made to protect it from falsification the more meaningless it is. It is a shades of grey issue not a black and white one.
No refutation of the Falsification Principle works. The principle has its enemies because it successfully disposes of religion and God.  Flew did not declare falsification to be definite. It is only probable.  It was not a dogmatic thing for him. It was more about being a method and definitely one that is the most likely to be correct.  But to me it is certain.