Sentence:  "Solitude, on the contrary, not only deprives us of both the past and the future, but always inclines the present hour to joyless melancholy, which sooner or later ends in something intractable, <WSD>Timonean</WSD>, (pardon the word) or perhaps more fatal." 
Meaning of the word marked with <WSD> tags:  Of a form of bitter misanthropy related to Timonism, like (Timon of Athens).