The Parable of the Invisible Gardener is a tale originally told by John Wisdom.
It was later developed in the university debate by Antony Flew, who made several important alterations such as changing the gardeners to explorers and making the original "long neglected garden" a clearing in the jungle.
Flew's main claim in using the parable is that religious believers do not allow anybody to "falsify" their assertions, instead they simply change their beliefs to suit the questioner.
Thus Flew concludes that religious believers cause God to "die the death of a thousand qualifications".
In Flew's version, the tale runs as follows: Once upon a time two explorers came upon a clearing in the jungle.