«Treatise on the Steppenwolf. This treatise, cited in full in the novel's text as Harry reads it, addresses Harry by name and strikes him as describing himself uncannily. It is a discourse on a man who believes himself to be of two natures: one high, the spiritual nature of man; the other is low and animalistic, a "wolf of the steppes". This man is entangled in an irresolvable struggle, never content with either nature because he cannot see beyond this self-made concept. The pamphlet gives an explanation of the multifaceted and indefinable nature of every man's soul, but Harry is either unable or unwilling to recognize this.»

Steppenwolf (originally Der Steppenwolf) is the tenth novel by German-Swiss author Hermann Hesse.

https://en.wikipedia.org/wiki/Steppenwolf_(novel)