|ΕΓΓΥΑ ΠΑΡΑ ΔΑΤΗ|
This saying is more cryptic than Know Thyself and Nothing overmuch.
A more literal translation is "A pledge, then calamity", where the Greek word for pledge refers to property or money laid down as collateral on a loan, or to bail someone out of jail. But such an interpretation is prosaic, and lacks the profundity and sapiential emphasis of the others.
A more plausible interpretation, then, is that given by Diogenes Laertius in his Life of Pyrrho. Diogenes saw in it an expression of Greek philosophical skepticism, in other words, "Beware of committing yourself to false opinion" or "Beware false certainty."
Recall that a Delphic oracle named Socrates the wisest of men. Socrates insisted that if he was wise, it was only because he recognized his own ignorance. In the Platonic dialogues, Socrates continually sought to expose the perils of false opinion, seeing it as one of the fundamental problems of human nature and society.