It's like a glass of pure water. If there is anything else in the glass, it can no longer be called a glass of pure water. Likewise, the presence of evil of any quantity or quality in a person disqualifies them from being good. Apple trees do not yield blueberries, and good men do not do evil things. So if we discern in our thoughts, words, and actions the presence of evil, we can know with absolute certainty that we, too, are evil.

Or is it supposed that hating each other, lying to one another, stealing from one another, murdering one another, failing to fulfill contract, covenant, and commitment to one another are things that should be considered good?