CS Lewis but here he is again. His works of fiction and non-fiction assume but never set out to prove the questionable notion of survival after death. The Biblical idea of the resurrection of the body contradicts the Greek and Indian ideas of the immortality of the soul.)
Souls exist in many, though not all, religious belief systems and therefore also in works of fantasy that assume the reality of ghosts or a hereafter. How many works by Poul Anderson?
SM Stirling's Church Universal and Triumphant perverts Eastern religions by teaching that some human beings are soulless and can lawfully be killed. Either every person has or is a soul or none have.
Do I believe that people are souls? No. Do I believe that people are "soulless"? No. The adjective is metaphorical, not metaphysical, and implies the Nazi concept of a life without value.