The falsification principle (atheism)

The falsification principle was developed by Karl Popper and part of the philosophy of science. Popper claimed that sicentific knowledge was gained once a hypotohesis was made, and the scientist would test this and would know under what circumstances the hypothesis could be proven false. If a scientist knew what they needed to see in order to agree their hypothesis would be rendered false, then this was meaningful. So if a scientist made a hypothesis that water boils at 100c, they would know that if they saw water boil at less than 100c, this would falsify the hypothesis, the fact that the scientist knows what would falsify the hypothesis gives the statements meaning. 

Anthony Flew took this approach and used it for religious language. Flew claimed that if there was absoulutely no situation in which a religious person would abandon their beliefs as false, then any religious statement was meaningless. Flew gave an example of a gardener:

“Two explorers come across a clearing in a jungle. It contains a mixture of weeds and flowers. One claims that there must be a gardener who comes to tend the clearing. The other denies it. They sit and wait, but no gardener appears, however they try to detect him.” One gardener continues to claim that there is a gardener; one who is invisible, inaudible, intangible and undetectable.

The gardener example is the same with religious people, they say God exists and he is all powerful and all loving. One could argue they've never seen God-Well thats because hes invisible. Then why is there so much evil in the world? Because God works in mysterious ways. There is no evidence to falsify their belief in God. The falsification principle would say if you're not willing under and circumstance to accept the falisfication of your belief, then all of your religious language is meaningless.