In order to disprove the assertion that all crows are black, one white crow is sufficient.

Keep the faculty of effort alive in you by a little gratuitous exercise every day.

There is nothing so absurd that it cannot be believed as truth if repeated often enough.

The greatest discovery of my generation is that a human being can alter his life by altering his attitudes.

Our theories are wedged and controlled as nothing else is. Yet sometimes alternative theoretic formulas are equally compatible with all the truths we know, and then we choose between them for subjective reasons. We choose the kind of theory to which we are already partial: we follow 'elegenace' or 'economy'

Wisdom is learning what to overlook.

The same is true of Love, and the instinctive desire to please those whom we love. The teacher who succeeds in getting herself loved by the pupils will obtain results which one of a more forbidding temperament finds it impossible to secure.