Full Idea
Agrippa's Trilemma offers three possible outcomes for a regress of justification: the chain goes on for ever (infinite); or the chain stops at an unjustified proposition (arbitrary); or the chain eventually includes the original proposition (circular).
Gist of Idea
Agrippa's Trilemma: justification is infinite, or ends arbitrarily, or is circular
Source
report of Agrippa (fragments/reports [c.60], §2) by Michael Williams - Without Immediate Justification §2
Book Reference
'Contemporary Debates in Epistemology', ed/tr. Steup,M/Sosa,E [Blackwell 2005], p.205
A Reaction
This summarises Ideas 1911, 1913 and 1914. Agrippa's Trilemma is now a standard starting point for modern discussions of foundations. Personally I reject 2, and am torn between 1 (+ social consensus) and 3 (with a benign, coherent circle).
Related Ideas
Idea 1911 Even if all known nations agree on a practice, there may be unknown nations which disagree [Sext.Empiricus]
Idea 1913 Is virtue taught, or achieved by practice, or a natural aptitude, or what? [Plato]