‘Despair, or folly?’ said Gandalf. ‘It is not despair, for despair is only for those who see the end beyond all doubt. We do not. It is wisdom to recognize necessity, when all other courses have been weighed, though as folly it may appear to those who cling to false hope.'”
– LOTR 269
Gandalf’s response to the Council of Elrond who believe destroying the Ring would be folly.