The Immortal Soul?
We should let the scriptures speak:
KJV Ezekiel 18:4 Behold, all souls are mine; as the soul of the father, so also the soul of the son is mine: the soul that sinneth, it shall die. (Eze 18:4 KJV)
KJV Matthew 10:28 And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell. (Mat 10:28 KJV)
Clearly the soul can die. Indeed the soul with the body can be destroyed in "hell".