Do we use them when we don't know the gender of the speaker?

Question

If I see an old person, I will help (him - them - both are correct).

This could be silly. However I don't know whether to choose him or them or both.

Answer 1

The traditional answer would be that if the sex of a singular noun referring to a person was unknown, the applicable pronoun was "he," "him," or "his," whichever was syntactically appropriate. Alternatively, you could say "he or she," "him or her," or "his or her." Those alternates, although acceptable, are seldom used because they are wordy.

In the last few decades, there have been efforts to replace the native third person singular pronouns with contrived ones on the basis that the supposition of a person of unknown sex being necessarily male is certainly unfounded and may be demeaning. (The demeaning aspect is of course open to dispute. My mother said that she had worked very hard to become Chairman of her department and certainly did not want to be confused with a piece of furniture or to have it implied that her sex was in any way relevant to her capacity to perform the duties of her position.)

Many people use "they," "them," or "their" as pronouns for singular nouns referring to people whose sex is unknown. I believe that this is so common, at least in the US, that it must be accepted as fully grammatical despite the apparent confusion in number. This rule does not apply to animals whose sex is unknown. In that case, the pronouns used are "it" and "its."

To get back to your example,

If you see an old person having difficulty crossing a busy street, you should help them

is perfectly acceptable and comprehensible in the US.