Interestingly, any misuse of justice is unjust, not foolish. This suggests that we evaluate errors by superiors differently from the errors of peers. For example one may safely ignore a friend's advice phrased as a command, but not the command of a judge in chambers.
Of all the vices, folly is one of the easiest to detect and condemn in others and one of the hardest to recognize within one's self. This is because much folly results from one's natural character, and detection of folly requires a more accurate self-appraisal than most people can perform. Also, fools often mistake their follies for virtue, or see a folly as a virtue.
Of course, when people do not recognize their folly, they repeat it. Thus the proverb, "As a dog returns to lick his vomit, so a fool returns to his folly."
A generic process to recognise one's past folly is to read biographies and try to recognise situations in which successful people's lives turned for the better. Then try to remember what one thought to one's self while making the wrong decision in a similar situation. Of course this process is far more useful for young people, but it has some value for anyone that's alive.
A generic process to avoid folly is to ask others' advice when making major decisions (i.e. anything involving more than a week of time, or the equivalent salary). One's foolishness may become apparent when more than one person picks a choice other than one's own. Compare the thoughts, and look for folly.
Folly is extremely hazardous; it probably kills most of us, whether by avoidable accidents or diseases brought by life-styles.
Folly is almost exactly the opposite of wisdom.
Examples include:
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