The Fathers of the Church all believed in "fiat" creation as in, "God said, 'Let there be light,' and there was light." Creationism has been reaffirmed by popes throughout history. Even those whose writings have been distorted to "prove" there is no conflict between the HYPOTHESIS of evolution and belief that God guided the evolutionary process warned of its dangers. For example, While Pope Pius XII did not forbid discussion of evolution among scientists and theologians, he very explicitly forbade its teaching in the papal encyclical, Humani Generis (August 1950):