The crossword solution for the term VOLTAIRE WAS ONE is DEIST, which is a five-letter word. Voltaire was a French Enlightenment writer, historian, and philosopher who was known for his deist beliefs. Deism is a philosophical belief that emphasizes the role of reason and observation in understanding the universe, as opposed to relying on religious teachings or divine intervention. Voltaire was one of the most influential figures of the Enlightenment and his deist beliefs were an important part of his philosophy.