The line, 'what doesn't kill you makes you stronger' that is said in Kelly Clarkson's pop song, 'Stronger (What Doesn't Kill You)' comes from the work of German existentialist philosopher, Friedrich Nietzsche. What Nietzsche actually wrote is, 'From life's school of war: what does not kill me makes me stronger.' The phrase comes from Nietzsche's highly influential Twilight of the Idols, which he intended as an introduction to his work. It has been paraphrased and revised many times in popular culture. Political conservative luminary G. Gordon Liddy changed it to be 'What doesn't kill us, makes us stronger,' and Liddy's reprisal has often been quoted as though it were Nietzsche's exact words.