That life is worth living is the most necessary of assumptions, and were it not assumed, the most impossible of conclusions.

George Santayana (1863-1952) Spanish-American poet and philosopher [Jorge Agustín Nicolás Ruíz de Santayana y Borrás]

The Life of Reason or The Phases of Human Progress, Vol. 1 “Reason in Common Sense,” ch. 10 (1905-06)
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