Where Seneca says something like:
To be good, it is not enough to be better than the worst.
I am looking for the correct preferably online reference.
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Bonitas non est pessimis esse meliorem.
translated as "goodness does not mean merely being better than the lowest"
in Epistles vol.2 LXXIX (Number 89, "On the rewards of scientific discovery"), Translated by Richard M. Gummere. The Loeb Classical Library. Cambridge, Mass.: Harvard UP, 1917-25.