In the spiritual state, a soul's very essence is enough to identify it.
As spirit-souls, we are obliged to complete our sojourn on the material plane. In her preamble to part two, Kirkudian, What happens after death? Scientific & Personal Evidence for Survival, author, Migęne Gonzalez-Wippler, writes that the second part of the book deals with the various incarnations of a spirit who calls himself Kirkudian. This highly evolved entity chose to write and tell his story, Kirkudian's story, of his various incarnations, on earth, and in other worlds.
Kirkudian explains that a soul's pilgrimage represents the sum of incarnations through which it must journey for its purification. When its cycle of incarnations ends, the spirit-soul is offered a choice. It may remain in whatever level of the astral plane its evolutionary path has prepared it for, or it may return to the material world of its choice as either a guide or protector of one of its inhabitants. In certain cases, the soul may choose to become the guide to the collective soul of the race. It may do so as valour, love, peace, faith, hope, compassion, or any of the many virtues that help material beings overcome their baser instincts.
Migęne Gonzalez-Wippler, What Happens After Death, Scientific & Personal Evidence for Survival, 1997, Llewellyn Publications, Minnesota, U. S. A., Part Two, Kirkudian, 127
The Pilgrim of the Cross at the End of His Journey | Thomas Cole (1801–1848) | Smithsonian American Art Museum