An important part of the Egyptian soul was thought to be the jb, or heart. The heart was believed to be formed from one drop of blood from the child's mother's heart, taken at conception. To ancient Egyptians, the heart was the seat of emotion, thought, will and intention. This is evidenced by the many expressions in the Egyptian language which incorporate the word jb. This word was transcribed by E. A. Wallis Budge as Ab.
In Egyptian religion, the heart was the key to the afterlife. It was conceived as surviving death in the nether world, where it gave evidence for, or against, its possessor. It was thought that the heart was examined by Anubis and the deities during the Weighing of the Heart ceremony. If the heart weighed more than the feather of Ma'at, it was immediately consumed by the monster Ammit.
A person's shadow or silhouette, Sheut (šwt in Egyptian), is always present. Because of this, Egyptians surmised that a shadow contains something of the person it represents. Through this association, statues of people and deities were sometimes referred to as shadows.
The shadow was also representative to Egyptians of a figure of death, or servant of Anubis, and was depicted graphically as a small human figure painted completely black. Sometimes people (usually pharaohs) had a shadow box in which part of their Sheut was stored.
As a part of the soul, a person's ren (rn 'name') was given to them at birth and the Egyptians believed that it would live for as long as that name was spoken, which explains why efforts were made to protect it and the practice of placing it in numerous writings. For example, part of the Book of Breathings, a derivative of the Book of the Dead, was a means to ensure the survival of the name. A cartouche (magical rope) often was used to surround the name and protect it. Conversely, the names of deceased enemies of the state, such as Akhenaten, were hacked out of monuments in a form of damnatio memoriae. Sometimes, however, they were removed in order to make room for the economical insertion of the name of a successor, without having to build another monument. The greater the number of places a name was used, the greater the possibility it would survive to be read and spoken.
The 'Bâ' (bꜣ) was everything that makes an individual unique, similar to the notion of 'personality'. (In this sense, inanimate objects could also have a 'Bâ', a unique character, and indeed Old Kingdom pyramids often were called the Bâ of their owner). The Bâ is an aspect of a person that the Egyptians believed would live after the body died, and it is sometimes depicted as a human-headed bird flying out of the tomb to join with the Ka in the afterlife.
In the Coffin Texts one form of the Bâ that comes into existence after death is corporeal, eating, drinking and copulating. Louis Žabkar argued that the Bâ is not part of the person but is the person himself, unlike the soul in Greek, or late Judaic, Christian or Muslim thought. The idea of a purely immaterial existence was so foreign to Egyptian thought that when Christianity spread in Egypt they borrowed the Greek word psyche to describe the concept of soul and not the term Bâ. Žabkar concludes that so particular was the concept of Bâ to ancient Egyptian thought that it ought not to be translated but instead the concept be footnoted or parenthetically explained as one of the modes of existence for a person.
In another mode of existence the Bâ of the deceased is depicted in the Book of Going Forth by Day returning to the mummy and participating in life outside the tomb in non-corporeal form, echoing the solar theology of Re (or Ra) uniting with Osiris each night.
The word bau (bꜣw), plural of the word ba, meant something similar to 'impressiveness', 'power', and 'reputation', particularly of a deity. When a deity intervened in human affairs, it was said that the Bau of the deity were at work [Borghouts 1982].
The Ka (kꜣ) was the Egyptian concept of vital essence, that which distinguishes the difference between a living and a dead person, with death occurring when the ka left the body. The Egyptians believed that Khnum created the bodies of children on a potter's wheel and inserted them into their mothers' bodies. Depending on the region, Egyptians believed that Heqet or Meskhenet was the creator of each person's ka, breathing it into them at the instant of their birth as the part of their soul that made them be alive. This resembles the concept of spirit in other religions.
The Egyptians also believed that the ka was sustained through food and drink. For this reason food and drink offerings were presented to the dead, although it was the kau (kꜣw) within the offerings that was consumed, not the physical aspect. The ka was often represented in Egyptian iconography as a second image of the king, leading earlier works to attempt to translate ka as double.
The Akh (Ꜣḫ "(magically) effective one"), was a concept of the dead that varied over the long history of ancient Egyptian belief.
It was associated with thought, but not as an action of the mind; rather, it was intellect as a living entity. The Akh also played a role in the afterlife. Following the death of the Khat (physical body), the Ba and Ka were reunited to reanimate the Akh. The reanimation of the Akh was only possible if the proper funeral rites were executed and followed by constant offerings. The ritual was termed: se-akh 'to make (a dead person) into an (living) akh.' In this sense, it even developed into a sort of ghost or roaming 'dead being' (when the tomb was not in order any more) during the Twentieth Dynasty. An Akh could do either harm or good to persons still living, depending on the circumstances, causing e.g., nightmares, feelings of guilt, sickness, etc. It could be invoked by prayers or written letters left in the tomb's offering chapel also in order to help living family members, e.g., by intervening in disputes, by making an appeal to other dead persons or deities with any authority to influence things on earth for the better, but also to inflict punishments.
The separation of Akh and the unification of Ka and Ba were brought about after death by having the proper offerings made and knowing the proper, efficacious spell, but there was an attendant risk of dying again. Egyptian funerary literature (such as the Coffin Texts and the Book of the Dead) were intended to aid the deceased in "not dying a second time" and to aid in becoming an akh.
Ancient Egyptians believed that death occurs when a person's Ka leaves the body. Ceremonies conducted by priests after death, including the "opening of the mouth (wp r)", aimed not only to restore a person's physical abilities in death, but also to release a Ba's attachment to the body. This allowed the Ba to be united with the Ka in the afterlife, creating an entity known as an Akh (ꜣḫ - "effective one").
Egyptians conceived of an afterlife as quite similar to normal physical existence — but with a difference. The model for this new existence was the journey of the Sun. At night the Sun descended into the Duat (the underworld). Eventually the Sun meets the body of the mummified Osiris. Osiris and the Sun, re-energized by each other, rise to new life for another day. For the deceased, their body and their tomb were their personal Osiris and a personal Duat. For this reason they are often addressed as "Osiris". For this process to work, some sort of bodily preservation was required, to allow the Ba to return during the night, and to rise to new life in the morning. However, the complete ꜣḫs were also thought to appear as stars. Until the Late Period, non-royal Egyptians did not expect to unite with the Sun deity, it being reserved for the royals.
The Book of the Dead, the collection of spells which aided a person in the afterlife, had the Egyptian name of the Book of going forth by day. They helped people avoid the perils of the afterlife and also aided their existence, containing spells to ensure "not dying a second time in the underworld", and to "grant memory always" to a person. In the Egyptian religion it was possible to die in the afterlife and this death was permanent.
The tomb of Paheri, an Eighteenth dynasty nomarch of Nekhen, has an eloquent description of this existence, and is translated by James Peter Allen as:
Your life happening again, without your ba being kept away from your divine corpse, with your ba being together with the akh ... You shall emerge each day and return each evening. A lamp will be lit for you in the night until the sunlight shines forth on your breast. You shall be told: "Welcome, welcome, into this your house of the living!