Full Idea
Against the Stoics, the Pyrrhonians argued that if someone presents a criterion of truth, then it will be important to determine whether it is the correct criterion.
Gist of Idea
If we need a criterion of truth, we need to know whether it is the correct criterion
Source
report of Pyrrho (reports [c.325 BCE]) by Robert Fogelin - Walking the Tightrope of Reason Ch.4
Book Reference
Fogelin,Robert: 'Walking the Tightrope of Reason' [OUP 2004], p.116
A Reaction
Hence Davidson says that attempts to define truth are 'folly'. If something has to be taken as basic, then truth seems a good candidate (since, for example, logical operators could not otherwise be defined by means of 'truth' tables).