I am not surprised that people are bored when they are alone; they cannot laugh when they are alone, for such a thing seems foolish to them. Is laughter, then, to be regarded as merely a signal for others, a mere sign, like a word? It is a want of imagination and dullness of mind generally as Theophrastus puts it, that prevents people from laughing when they are alone. The lower animals neither laugh when they are alone nor in company.
Nyson, the misanthropist, was surprised as he was laughing to himself by one of these people, who asked him why he laughed when he was alone. “That is just why I was laughing,” was the answer.
Arthur Schopenhauer. From Dircks’s translation of Essays of Schopenhauer.
Biblioklept 