1. It means that when you look at evil, evil is also looking at your heart like a mirror. Human nature is complex. There is no pure good or pure evil. In many cases, the two are interchangeable or coexist.
2. This sentence comes from the famous German philosopher Friedrich Wilhelm Nietzsche.
3. The original text is: "Wer mit Ungeheuern k?mpft, mag zusehn, dass er nicht dabei zum Ungeheuer wird. Und wenn du lange in einen Abgrund blickst, blickt der Abgrund auch in dich hinein." That is "Fight with the dragon for too long, and you will become a dragon; stare into the abyss for too long, and the abyss will stare back."
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Friedrich Wilhelm · Nietzsche (German: Friedrich Wilhelm Nietzsche, October 15, 1844 - August 25, 1900, aged 55), German, famous philosopher, linguist, cultural critic, poet, composer, and thinker , is considered the founder of modern Western philosophy. His works have provided extensive criticism and discussion in the fields of religion, morality, modern culture, philosophy, and science. His writing style is unique, often using aphorisms and paradoxes. Nietzsche had a great influence on the development of subsequent generations of philosophy, especially existentialism and postmodernism.
Before he began to study philosophy, Nietzsche was a philologist. At the age of 24, Nietzsche became a professor of classical philology in the German-speaking area at the University of Basel in Switzerland, specializing in ancient Greek and Latin literature. But he resigned in 1879 due to health problems and has been suffering from mental illness ever since. Nietzsche suffered a nervous breakdown in 1889 and never recovered. He lived under the care of his mother and sister until his death in 1900.
Nietzsche's major works include "The Will to Power", "The Birth of Tragedy", "An Untimely Investigation", "Thus Spoke Zarathustra", "Philosophy in the Age of Greek Tragedy", "On the Genealogy of Morality", etc.
Reference: Baidu Encyclopedia entry? Friedrich Wilhelm Nietzsche (famous German philosopher)