Voltaire's take on Islam

"But that a camel-merchant should stir up insurrection in his village; that in league with some miserable followers he persuades them that he talks with the angel Gabriel; that he boasts of having been carried to heaven, where he received in part this unintelligible book, each page of which makes common sense shudder; that, to pay homage to this book, he delivers his country to iron and flame; that he cuts the throats of fathers and kidnaps daughters; that he gives to the defeated the choice of his religion or death: this is assuredly nothing any man can excuse, at least if he was not born a Turk, or if superstition has not extinguished all natural light in him."  

(Referring to Muhammad, in a letter to Frederick II of Prussia (December 1740), published in Oeuvres complètes de Voltaire, Vol. 7 (1869))