In religions and some philosophical systems, the idea of an immaterial element to human beings. The soul is the inner, spiritual principle which is the source of life and all living functions.
The soul, together with the material body, constitutes the complete human being. Still, the soul is in many systems understood as a quality that can exist without the human body. In many religious systems, the soul is that part of a human being that can take part in the divine by survival of the corporeal death. In religions like Christianity and Islam, however, there is no contradiction between soul and material body, the both will be part of the eternal afterlife.
In some belief systems, a human being can lose the soul, or have it stolen, which is then understood as resulting in disease or insanity.
The idea of the soul goes deep back in human thinking. Still, it seems that Gnostic thinking around the seed of light trapped in the physical body has been the model of the concept of soul in major religions like Christianity and Islam.
Zoroastrianism has the concept of a soul, a soul that is the part of the human being that survives into the Afterlife.
Judaism had for very long no idea of the soul as such, its concept has been developed since the Middle Ages. Soul is understood as the principle of life, that aspect of a human being that survived when the body decayed.
In Christianity, the idea of a soul came by the influence of the philosophies of Plato and Aristotle. In general, Christianity promotes the idea that resurrection will happen to the complete human being, body and soul together. The idea of the soul imprisoned in the body survived until the 13th century, when Thomas Aquinas redefined the body and soul into two elements of a single substance.
The ideas of Islam corresponds to that of Christianity. Soul is clearly mentioned, but not in the sense that the body represents the opposite quality of the soul. The soul is rather understood as that what brings life the material body.
Alevism has no clear definition of soul, in the few cases where soul is mentioned it seems to express spirit and liveliness.
Being a religion of reincarnation, soul is clearly defined in Ahl-e Haqq. The soul passes, following death, from one material body to the next. Liberation happens through several life spans (see Soul and its liberation).
The concept of a soul is vital to the theology of Yazidism. The greatest punishment that can be inflicted upon a member of the faith is expulsion, which will mean that ones soul is lost forever.
Being a religion of reincarnation, soul is clearly defined in Isma'ilism. The soul is what human beings hope to liberate from the cycle of reincarnation, to allow it to return to the spheres of the divine.
Being a religion of reincarnation, there is much focus on the soul in Druze religion. All souls are reborn as humans, good as well as bad. Good people have a more fortunate rebirth than bad people. The soul is represented with the red colour in the Druze star (can be seen in the article on Druze religion).
In Baha'i the fundamental quality to a human being is an invisible, rational and eternal soul. Souls can only reside with humans. By a good life the soul can grow, and the soul lives on after the corporeal death. It is the soul that enters the great journey of the afterlife, trying to come as close to God as possible.
Ancient Egyptian religion
The concept of a soul in Ancient Egyptian religion is richly developed and described in details. The soul consists of the ba, akh and the ka. Ka is the quality one is born with and linked to family, akh is the spirit of the deceased, whereas the ba is the most unclearly defined and seem to be something in between. In the afterlife, the ka stays near the body, the ba proceeds to the region of the dead. There was no conflict with the three categories, they were rich expressions of the complexity of spirit or soul of a human being.
There seems not to have been any concept of a soul to neither Sumerian nor Babylonian and Assyrian religions. The afterlife was in the existence of ghosts, but such ghosts do not correspond to the concept of soul.
Canaanite and Phoenician religions
There seems not to have been any concept of soul in Canaanite and Phoenician religions. Even afterlife is devoid of categories that come near that of soul.
Hittite religion defined humans beings as body and soul together, but soul was of importance mainly in the earhtly existence. There was little to expect of an afterlife for the soul of the deceased.
Being one of the original Gnostic religions, Manichaeism has the concept of a seed of light. This concept is largely related to that of a soul, but there is a major difference in it being an estranged element to the body, and impersonal.