The fourth person is a variety of the third person sometimes used for indefinite referents, such as “one” in “one should not do that”.
It is a grammatical person in some languages distinct from first, second, and third persons; it is always semantically translated in English.
In some languages the fourth person is indicated by a special grammatical marker. In general linguistics, this marker is know as the obviation.
Potawatomi (a language spoken by the native Algonquin people of central Canada, one of a closely related group of languages and dialects of the Algonquian branch of the Algic language family) is notable for having two degrees of obviation, simply known as obviation and further obviation.
An obviative is a grammatical marker that distinguishes between a non-salient (obviative) third person referent from a more salient (proximate) third person.
“He cuddled his [another’s] rabbit.”
A further obviative referent is deemed even less salient than the obviative referent and is marked by an additional obviative suffix.
/proximate/ “rabbit” = waposo
/obviative/ “rabbit” = waposo-n
/further obviative/ “rabbit” = waposo-n-un
“The past is always tense, the future perfect.” – Zadie Smith