Full Idea
An assertion is logically equivalent to denying its opposite, but claims about a 'gardener', or God, make neither claims nor denials of anything, so no evidence can count against the claim, or for it.
Gist of Idea
Claims about God don't seem to claim or deny anything tangible, so evidence is irrelevant
Source
report of Antony Flew (Theology and Falsification [1950]) by PG - Db (ideas)
Book Reference
'The Existence of God', ed/tr. Hick,John [Macmillan 1964], p.226