The Khu thus forms a link between men and the gods, and participates in the divine nature. It is the soul regarded as a godlike essence, as coming down from heaven rather than as mounting up towards it. It is not only disembodied, but needs the body no longer; it belongs to the Ka, which still lives and moves, and not to the mummified corpse from which the vital spark has fled. It waits on the god of the dead, not on the dead themselves.
It seems probable, therefore, that in the part of Egypt in which the doctrine of the Khu grew up, mummification was not practised; and the probability is strengthened by the fact that, before the rise of the Third Dynasty, embalming was apparently not frequent in Upper Egypt, even in the case of the kings. But, however this may be, one thing is certain. The conception of the Khu cannot have originated in the same part of the country, or perhaps among the same element in the population, as a parallel but wholly inconsistent conception which eventually gained the predominance. According to this conception, the imperishable part of man which, like the Ka, passed after death into the other world, was the Ba or "soul." Like the Khu, the Ba was pictured as a bird; but the bird is usually given a human head and sometimes human hands.(29) But, while the Khu was essentially divine, the Ba was essentially human. It is true that the Ba, as well as the Khu, was assigned to the gods--Ra of Heliopolis was even credited with seven; but whereas man possessed a Khu or luminous soul because he was likened to the gods, the gods possessed a Ba because they were likened to men.
The relation between the two is brought out very clearly in the philosophy of the so-called Hermetic books, which endeavoured to translate the theology of Egypt into Greek thought. There we are told that the Khu is the intelligence ({ ~GREEK SMALL LETTER NU~}{ ~GREEK SMALL LETTER OMICRON~}{ ~GREEK SMALL LETTER UPSILON WITH PERISPOMENI~}{ ~GREEK SMALL LETTER FINAL SIGMA~}), of which the Ba or soul ({ ~GREEK SMALL LETTER PSI~}{ ~GREEK SMALL LETTER UPSILON~}{ ~GREEK SMALL LETTER CHI~}{ ~GREEK SMALL LETTER ETA WITH OXIA~}) is as it were the envelope. As long as the soul is imprisoned in the earthly tabernacle of the body, the intelligence is deprived of the robe of fire in which it should be clothed, its brightness is dimmed, and its purity is sullied. The death of the body releases it from its prison-house; it once more soars to heaven and becomes a spirit ({ ~GREEK SMALL LETTER DELTA~}{ ~GREEK SMALL LETTER ALPHA~}{ ~GREEK SMALL LETTER IOTA WITH OXIA~}{ ~GREEK SMALL LETTER MU~}{ ~GREEK SMALL LETTER OMEGA~}{ ~GREEK SMALL LETTER NU~}), while the soul is carried to the hall of judgment, there to be awarded punishment or happiness in accordance with its deserts.(30) The Khu, in other words, is a spark of that divine intelligence which pervades the world and to which it must return; the Ba is the individual soul which has to answer after death for the deeds committed in the body.