It is interesting that in some areas of Slavic speaking countries, if you walk into a restaurant, when asked how many in a group are to dine, you might be asked "how many souls". I'm thinking of the Bulgarian tradition of asking "Колко души сте?" If two persons the answer would be "Две души." Is this true among Russian speakers in any of the regions of Russia?
"Soul" in English is generally used only by someone who has some sort of religious belief (I say generally, because it is used poetically more widely).
When someone is simply making the mind/body distinction, they commonly talk about "spirit".
Does душа cover both these contexts?
"Spirit" is usually дух. Some examples to give an idea of its semantic field: Holy Spirit — свято́й дух, evil spirits — злы́е ду́хи (careful with the stress: духи́ means "perfume"), fighting spirit — боево́й дух, the spirit of the law — дух зако́на, in the spirit of sth — в ду́хе чего-либо, etc.
However, when talking about the mind/body distinction, both are possible, I think. Maybe it depends on a particular context. For example, "young in spirit" can be both мо́лод ду́хом and молод душо́й / в душе́ (again, NB the stress: в ду́ше is "in the shower").
Often Russian uses душа where English uses "heart": at heart — в душе́ (I'm a romantic at heart — В душе́ я рома́нтик), in someone's heart of hearts — в глубине́ души́ ("in the depth of soul"), to one's heart's content — ско́лько душе́ уго́дно ("as much as the soul wishes"), from the bottom of one's heart — от всей души́ ("from all the soul") and, no doubt, many others.
Yes, as I suspected, this is getting complicated. The division between related concepts lies in different places in our two languages.
Am I right that дух is the usual term for a ghost? (i.e. the supernatural remnant of a dead person)
And that Russians also use the heart metaphorically, as the location of genuine feeling? (c.f. "straight from the heart")
The usual term for a ghost is при́зрак or привиде́ние. (Not sure about the difference between these two. We usually say "someone's призрак", but "В этом доме живёт привидение" — "This house is haunted" or "Ты веришь в привидения?" — "Do you believe in ghosts?")
Yes, сердце is also used. To say "sincerely", you could use either от всей души or от всего́ се́рдца. Серде́чный приём — a cordial/warm/kind welcome.
While I understand this and appreciate the intent of the rules. If they don't want people to talk about the function of a soul, then perhaps they shouldn't have more than 30% of the questions in this chapter be about a soul.
That said, I'm glad that since they insisted on including the subject, they put it in the body parts section and not a separate spiritual/religious section.