The two beings are Nikolai Stavrogin and Shatov, and this passage is from Dostoevsky’s Demons, Part II, Chapter 6:
Stavrogin’ is an atheist. His ridiculous actions in Dostoevsky’s
Demons include pulling a high social standing man by the nose at a local bar, kissing another man’s wife at her own party, and biting the ear of the territorial governor. Such wild antics and others cause him to be diagnosed with insanity. In this excerpt he’s speaking with Shatov, his former student, who was expelled from school due to an unknown scandal. A one time a radical socialist, Shatov converts to a Russian idealist.

These two beings are, as Dostoevsky says, converged in infinity. In Russian the word is беспредельности. What does that mean? If there is one subject matter of Dostoevsky’s books, or rather testaments (books is somehow not enough of a word for his writings!) this might be best said as he’s writing about all of us, “beings converged in infinity.” That’s all of us, and Dovtoevsky was one of the first to realize this.