Anthony Flew famously wrote:
Once upon a time two explorers came upon a clearing in the jungle. In the clearing were growing many flowers and many weeds. One explorer says, "Some gardener must tend this plot." The other disagrees, "There is no gardener." So they pitch their tents and set a watch. No gardener is ever seen. "But perhaps he is an invisible gardener." So they set up a barbed-wire fence. They electrify it. They patrol with bloodhounds. (For they remember how H. G. Well's The Invisible Man could be both smelt and touched though he could not be seen.) But no shrieks ever suggest that some intruder has received a shock. No movements of the wire ever betray an invisible climber. The bloodhounds never give cry. Yet still the Believer is not convinced. "But there is a gardener, invisible, intangible, insensible, to electric shocks, a gardener who has no scent and makes no sound, a gardener who comes secretly to look after the garden which he loves." At last the Sceptic despairs, "But what remains of your original assertion? Just how does what you call an invisible, intangible, eternally elusive gardener differ from an imaginary gardener or even from no gardener at all?"
i) With whom is Flew shadowboxing? Is this directed at theological noncognitivism? Perhaps he's responding to modernist theologians who say God is ineffable. God is indefinable. He transcends our conceptual categories. There's no analogy between God and human words or concepts. If that's his target, then I think his parable scores a direct hit.
ii) But at another level, his parable suffers from an egregious blindspot. You don't need to empirically detect a gardener to infer a gardener. You don't motion detectors or spectrometry to smoke out the presence of a gardener. Rather, you infer the gardener from the garden. You infer the gardener from his effects. Flowerbeds don't weed themselves. Orchards don't thin themselves. Trees don't grow in rows, much less even-spaced rows. A well-tended garden implies the existence of a gardener. The garden itself is evidence for the gardener. You don't need direct evidence for the gardener, since the garden furnishes indirect, but unmistakable evidence for the gardener. Moreover, that's analogous to many theistic proofs. So in that respect, his parable is counterproductive.