believed to be mere sheaths,

[keannu]

This is quite an interesting religious topic. Typing this, I realized "instinctively" might mean the people(parents)'s instinct who abandon the children. I wondered what "mere sheaths" meant, but I guess some children showed some divine characteristics, while others didn't by, for example, fussing around too much or looking stupid, whatever. I don't know if my guess is right.

is94
ex)What did the Greeks see in a small child between birth and the change of teeth? They saw a being sent to earth from spiritual heights...The Greeks considered it important to recognize, in children up to the seventh year, that the physical body holds a spirit being who has descended...People exposed and thus killed the children who were instinctively believed to be mere sheaths, not expressing a true spirit being in their physical nature. This was the result of rigidly adhering to the belief that the physical human being during the first seven years of life is the garment of a divine spirit being.

 

[BobK]

I'm not sure that there's anything to discuss here, on the subject of language - except to say that 'sheath' is a very unusual word to use in this context, and implies extreme religious beliefs which are not for discussion here, however interesting you may find them.

b

 

[keannu]

I'm not interested in it too much. The thing is I have to explain it to some people as my responsiblity. But if it's a unique religious one, I will just tell them so.

 

[Barb_D]

The context suggests that they believe these children to be only the clothes of these spiritual beings but that the spiritual beings aren't actually inside them. How they come to this conclusion is anyone's guess. There is no reason to think that being fussy or looking a certain way is a reason.