It was the aim of the author in this study to collect, classify and analyze the various references made in the works of Alfonso X, el Sabio, to the beliefs and superstitions, of the Spaniard of that day, with reference to the supernatural. It is hoped that it will be possible in this way to reach a better understanding of the attitude of the Spanish people toward the supernatural in general and thus to acquire a more complete appreciation of that early period in the nation's life.