I have dwelt thus long on the doctrine of the Ka or double on account both of its importance and of the difficulties it presents to the modern scholar. Its discovery by Professor Maspero and Sir P. Le Page Renouf cleared away a host of misconceptions, and introduced light into one of the darkest corners of Egyptian religion(26). And however strange it may seem to us, it was in thorough accordance with the simple logic of primitive man. Given the premisses, the conclusion followed. It was only when the Egyptian came to progress in knowledge and culture, and new ideas about his own nature were adopted, that difficulties began to multiply and the theory of the Ka to become complicated.
Among these new ideas was that of the Khu or "luminous" part of man. On the recently discovered monuments of the early period, the Khu holds a place which it lost after the rise of Memphite influence with the Third Dynasty. We find it depicted on the tombstones of Abydos embraced by the down-bent arms of the Ka. The Khu, therefore, was conceived of as comprehended in the human Ka, as forming part of it, though at the same time as a separate entity. It was, in fact, the soul of the human Ka, and was accordingly symbolised by the crested ibis(27). It may be that it was in the beginning nothing more than the phosphorescent light emitted by decaying vegetation which the belated wayfarer took for a ghost; the _ginn_ (_jinn_) of the modern Egyptian fellah are similar lights which flash up suddenly from the ground. But the earliest examples of its use on the monuments are against such an ignoble origin, and suggest rather that it was the glorified spirit which mounted up like a bird in the arms of its Ka towards the brilliant vault of heaven. It is not until we come to the decadent days of the Greek and Roman periods that the Khu appears in a degraded form as a malignant ghost which enters the bodies of the living in order to torment them. No traces of such a belief are to be found in older days. The Pyramid texts speak of "the four Khu of Horus," "who live in Heliopolis," and were at once male and female, and of the Khu who brandish their arms and form a sort of bodyguard around the god of the dead. They are identified with the fixed stars, and more especially with those of the Great Bear, and in the euhemeristic chronicles of Egyptian history they become the "Manes" of Manetho, the semi-divine dynasty which intervened between the dynasties of the gods and of men.(28)