The subject quotation is taken from The Mysterious Stranger, an unfinished novella by Mark Twain. Although Twain penned several different versions of the tale, it is clear that his intention for this story was to examine the philosophical concept of solipsism, which is the belief that while human beings can be fairly certain they exist, they cannot be certain of anything else. According to that school of thought, knowledge of things outside of one’s own existence is impossible to acquire.
Thinkers like French Philosopher René Descartes relied on this theory in his formulation of Cartesian Skepticism by which he doubted the existence of the things he observed in nature. In his famous conclusion, cogito ergo sum (I think, therefore I am), Descartes doubted everything other than the existence of one’s self.
Toward the end of his life, Mark Twain adopted a nihilistic outlook toward life, probably due to severe personal traumas he suffered with regard to his family. He generally rejected established social conventions and beliefs in the areas of morality and religion. This is reflected in The Mysterious Stranger where his characters are subjected to feats of magic that the author appears to equate to religious fanaticism and are exposed to anti-Christian views of the world.
Twain takes the concept of solipsism beyond the traditional historical philosophical definition. He argues that even the self is unknowable:
Nothing exists; all is a dream. God—man—the world—the sun, the moon, the wilderness of stars—a dream, all a dream; they have no existence. Nothing exists save empty space—and you!
Narrator Theodor Fischer himself does not exist. He is but a magical dream, as is everything else in the world. His observations, perceptions, and even the tale he narrates are all simply illusions.
Unfortunately, since the author died before completing his final version of the novella, the literary world remains uncertain as to how Twain would have integrated his extreme philosophical perspective with modern-day rationality, and we are left with the author’s internal struggle with the nature of reality. The questions he raised in the subject quotation are simply unsolvable.