A Soul is an elusive, very abstract, subjective and personal concept that can vary greatly from culture to culture. It can be described as the lifeforce, or spiritual essence of a living being. Some call the soul a spirit, which is then described as the ghost is it's host perishes, and the soul leaves the body. Most people believe that the loss, eviction, or death of a soul is one of the primary differences notable the moment a person ceases being a person, and starts being a Zombie. As stated, these beliefs are far from unanimous, and likely unconfirmable.
During a times of war or zombie outbreak, thoughts of death are usually unavoidable for all people. Many people struggle with their consciences and/or their understanding of life's meaning. Talk of souls, spirits, heaven and hell are all commonplace. It is advisable to only continue such conversations for as long as it is helpful, as even these seemingly innocent and being conversations can have damaging effects to morale or mental health if taken too far.