The ideas of 19th-century German philosophers Max Stirner and Friedrich Nietzsche have often been compared, and many authors have discussed apparent similarities in their writings, sometimes raising the question of influence. In Germany, during the early years of Nietzsche's emergence as a well-known figure, the only thinker discussed in connection with his ideas more often than Stirner was Schopenhauer. It is certain that Nietzsche read about Stirner's book The Ego and Its Own (Der Einzige und sein Eigentum, 1845), which was mentioned in Lange's History of Materialism (1866) and Eduard von Hartmann's Philosophy of the Unconscious (1869), both of which young Nietzsche knew very well. However, there is no irrefutable indication that he actually read it, as no mention of Stirner is known to exist anywhere in Nietzsche's publications, papers or correspondence.
And yet as soon as Nietzsche's work began to reach a wider audience the question of whether or not he owed a debt of influence to Stirner was raised. As early as 1891 (while Nietzsche was still alive, though incapacitated by mental illness) Eduard von Hartmann went so far as to suggest that he had plagiarized Stirner. By the turn of the century the belief that Nietzsche had been influenced by Stirner was so widespread that it became something of a commonplace, at least in Germany, prompting one observer to note in 1907 "Stirner's influence in modern Germany has assumed astonishing proportions, and moves in general parallel with that of Nietzsche. The two thinkers are regarded as exponents of essentially the same philosophy."
Nevertheless, from the very beginning of what was characterized as "great debate" regarding Stirner's possible influence on Nietzsche — positive or negative — serious problems with the idea were noted. By the middle of the 20th century, if Stirner was mentioned at all in works on Nietzsche, the idea of influence was often dismissed outright or abandoned as unanswerable.
But the idea that Nietzsche was influenced in some way by Stirner continues to attract a significant minority, perhaps because it seems necessary to explain in some reasonable fashion the often-noted (though arguably superficial) similarities in their writings. In any case, the most significant problems with the theory of possible Stirner influence on Nietzsche are not limited to the difficulty in establishing whether the one man knew of or read the other. They also consist in establishing precisely how and why Stirner in particular might have been a meaningful influence on a man as widely read as Nietzsche.