. >> host: university of wisconsin professor jennifer ratner-rosenhagen, who was frederick nietzsche? >> guest: he was a 19th century german philosopher who wrote many, many, many, many books on philosophy and all sorts of different forms. and all of them some after riskic, some essayistic, some longer formally teaks, and all of them -- critiques, and all of them had something to do with the challenge of universal truth. so he took as his enemy the notion of universal truth, and pretty much all of his work has something to do with his effort to tear it down, excavate it, look at the history of that idea and to show that anything that we take to be universals like, oh, god -- [laughter] are human creations. but they're not rooted in nature or necessity, they're not mirrors of reality. >> host: he wrote at one time god is dead -- >> guest: and he wrote that god is dead. and this first makes its appearance in his gay science. and in it the gay science -- in it, it's an aphorism, and it's called the madman. and so the aphorism is he's playing with this idea that a madman runs into the tow