Theorem. Let $S$ be an infinite set, let $\varphi : S \rightarrow S’$ be a bijective mapping from the set $S$ onto a proper subset $S’$ of the set $S$, let $a$ be an element of the set $S \setminus S’$, and let $N := \overline{ \{ a \} }$ be the chain generated by the set $\{ a \}$.