In class, I briefly described Flew's Gardener Example. Flew used this example to demonstrate how a seemingly substantive claim can be stripped of meaning by a process of qualification. Flew: Death by a Thousand Qualifications
In Flew's view, to qualify a claim is to amend it in such a way as to render it compatible with something which apparently showed the claim to be false. For example, the believer amends the claim about the gardener to a claim about an invisible gardener in order to make the claim that the gardener exists compatible with the fact that no gardener has been seen walking the grounds.
The process of qualification can be halted at a stage where something remains of the original assertion. That is, qualifying a claim doesn't always strip away its meaning. Qualification is a danger, however, since if taken too far, nothing remains that will show the claim to be false (that's just the point of qualification after all). And according to Flew, if there is nothing that will show the claim to be false, then nothing is said. (Think of the gardener again.)
Flew thinks that theistic propositions are in special danger of dying by qualification. He specifically considers the way in which "God cares for us" gets robbed of meaning when the theist qualifies it to deal with apparent counterexamples. That is, in response to the problem of evil the theist doesn't allow any apparent counterexample to her claim about God's love count as evidence against her view. Thus, there's nothing left at the end to the claim that "God loves us" because nothing has been allowed to show that the claim is false.
It is an open question, however, whether Flew is right that theistic propositons always are qualified to a point that they are rendered meaningless.