It is from the epithet of a parable, explaining that a fool waits for the stream to stop before crossing, while a wise man forgoes comfort and crosses anyway.
- "Have the courage to think for yourself"
- "Have courage to use your own reason", in the context of committing to tasks that need to be embarked upon, however unpleasant or awkward.
- Immanuel Kant described it as the motto of the Enlightenment in his essay "What Is Enlightenment?".
- It is a frequently used motto for academic institutions.