Definition and understanding of "Soul" by various religions. According to Joseph Campbell, the soul is where the inner and outer worlds meet.

1. THE SOUL
Soul, an essentially western concept, may be defined as the spiritual or eternal part of a
living being. It is separate from the physical body and embodies one’s consciousness and
personality. Soul is believed to live on after a person’s physical death.
In India, the ancient sages realized that human beings exist only because of an inner
power source in each one, which they named the JEEVATMAN. The Jeevatman is an
integral part of the universal power source, The PARAMATMAN, or, GOD. The human
body comes from the five elements of earth, and it goes back to them when the person
dies. Besides the physical body, we have the mind, which is not physical or gross, but
controls all our actions. The mind comes from God, and must eventually go back to it.
The mind functions only because of the presence of Jeevatman in the body. The mind
gets involved in worldly matters, and acquires good or bad influences as results of good
or bad actions. When one dies, his mind separates from the body and reincarnates in
another body, and more influences are acquired. This cycle of birth and death continues
till the mind gets rid of all its influences, by following a spiritual path and realizing that it
is not different from God, at which time it gets liberated and joins the Paramatman. While
the mind gets affected by worldly matters or Maya, the Jeevatman is always pure and is
unaffected. There is no change whatsoever in the Jeevatman, which is the same as the
infinite, absolute, eternal Paramatman. The western concept of ‘Soul’ must be the same
as the Hindu concept of human mind powered by Jeevatman.
Sikhs believe that ‘Soul’ is an integral part of the Universal Soul or God.
Buddhism accepts Soul as an incorporeal component in living things that can continue
after death, but does not believe it to be permanent. As thought changes from moment to
moment, one’s soul now is different from what it was few moments back. But the soul
maintains its individual identity through all these changes.
Greek philosophers like Socrates and Plato considered the ‘Soul’ as the essence of a
person which is an external occupant of our body. Only bodies die, but soul is eternal.
Aristotle thought soul to be the core or essence of a living being, its activity or its life..
Christianity believes that ‘Soul’ is the breath of life given by God to beings which were
created out of earth. Upon death the body goes back to earth while the soul returns to God
who gave it in the first place.