Who said “The deepest definition of youth is life as yet untouched by tragedy.”?

“Ask the young. They know everything.”

“Those whom the gods love grow young.”

“Young people need models, not critics...”

“Even the youngest of us may be wrong sometimes.”

“What Youth deemed crystal, Age finds out was dew.”

“Without adventure civilization is in full decay.”

“We think in generalities, but we live in detail.”

“Life is an offensive, directed against the repetitious mechanism of the Universe.”

“The art of progress is to preserve order amid change, and to preserve change amid order.”

“Civilization advances by extending the number of important operations which we can perform without thinking.”

“Familiar things happen, and mankind does not bother about them. It requires a very unusual mind to undertake the analysis of the obvious.”