Full Idea
If each of you says how many teeth the other has, and when they are counted we find you do know, we will believe your other claims as well.
Gist of Idea
Say how many teeth the other has, then count them. If you are right, we will trust your other claims
Source
Plato (Euthydemus [c.385 BCE], 294c)
Book Reference
Plato: 'Early Socratic Dialogues', ed/tr. Saunders,Trevor J [Penguin 1987], p.353
A Reaction
This is the clairvoyant problem for reliabilism, if truth is delivered for no apparent reason. Useful, but hardly knowledge. HOW did you know the number of teeth?