The Ancient Greeks used the same word soul for 'alive' as for
'ensouled'. So the earliest surviving Western philosophical view might
suggest that the terms soul and aliveness.
Francis M. Cornford quotes Pindar in saying that the soul sleeps whilst
the limbs are active, but when man is sleeping, the soul is active and
reveals in many a dream "an award of joy or sorrow drawing near".
Plato, drawing on the words of his teacher Socrates, considered the soul
as the essence of a person, being, that which decides how we behave. He
considered this essence as an incorporeal, eternal occupant of our
being. As bodies die the soul is continually reborn in subsequent
bodies.
The concept of soul has provided the basis for the major theories of
creationism, traducianism and pre-existence. According to creationism,
each individual soul is created directly by God, either at the moment of
conception, or some later time (identical twins arise several cell
divisions after conception, but no one would deny that they have whole
souls). According to traducianism, the soul comes from the parents by
natural generation. According to the pre-existence theory, which is not
widely held by Christians, the soul exists before the moment of
conception.
Researchers, most notably Ian Stevenson and Brian Weiss have studied
reports of children talking about past-life experiences. Any evidence
that these experiences were in fact real would require a change in
scientific understanding of the mind or would support some notions of
the soul.
In recent decades, much research has been done in near-death
experiences, which are held by many as evidence for the existence of a
soul and afterlife. Visit any good book shop and you will find a
good number of books dealing with rebirth cases.
Acceptance of the concept of soul amounts to acceptance of other beliefs
associated with them. This makes the atheists to reject the concept
of soul.
"Modern biologists, unlike the ancient makers of myths, know that all
the phenomena of living systems can be reduced to physical and chemical
terms. They have no evidence of any 'vital force' or mystical spirit
and no need to seek for such. They recognize the fully alive body and
the newly dead body to be but two arbitrary points along a continuum of
decreasing organization".
http://www.atheists.org/Atheism/mind.html
In his book Consilience, E. O. Wilson took note that sociology has
identified belief in a soul as one of the universal human cultural
elements. Wilson suggested that biologists need to investigate how
human genes predispose people to believe in a soul.
Daniel Dennett has championed the idea that the human survival strategy
depends heavily on adoption of the intentional stance, a behavioral
strategy that predicts the actions of others based on the expectation
that they have a mind like one's own. Mirror neurons in brain regions
such as Broca's area may facilitate this behavioral strategy. The
intentional stance, Dennett suggests, has proven so successful that
people tend to apply it to all aspects of human experience, thus leading
to animism and to other conceptualizations of soul.
A counterargument (from Keith Sutherland, among others) points out that
just because the brain has regions that deal with colour and other
aspects of vision, one does not argue that the genes produce an area to
promote the illusion of a blue sky. By analogy, if there is a 'God
sense' just as there is a sense of vision, it seems to argue for the
objective existence of an extra-mundane reality.