From the journals of Darien Cliftwood, Euthanatos mage:

My Tradition knows/believes (the two of course are hard to parse
among we Awakened) that the only things which truly exists in the
world are human minds and souls. Reality as we understand it is a
construct of the collective consciousness, a dream all humans have
agreed to dream and treat as being real so that they may have a
common framework of experiences to bind them. Such binding is
necessary for the health of the human mind; the task of defying
natural Oblivion by choosing to exist is a hefty burden, and when one
does not have the aid of the rest of one's kind in carrying it,
feelings of loneliness and rejection and various neuroses spread
through the mind like cracks in a solitary wall upon which too much
weight is placed. We may like to think we desire infinite power,
complete freedom to do what we wish with no confining basis of
reality to prohibit us from opting to fly or shoot fire from our
eyes, but in truth, without the rest of the world to provide us with
some basis in fact on which to default, we would eventually falter
under the force of our travails, or even from triumphs which
overshoot their mark and prove unsatisfying, and would plunge into an
abyss of despair which has no bottom.

So in defining reality as the safety net upon which all minds walk in
order to find each other, we can easily see that the Restless Dead
are those humans who have slipped through the mesh. It is
inevitable, of course, that we felt the need to define a reality in
which lives begin, as our own lives did, and that this necessitates
we also allow them to end, else the population would increase
unchecked forever and we would soon be lost in a sea of identical
individuals containing no uniqueness or meaning. So we opt instead
to be capable of dying, surrendering the seed of our individuality so
that it might sprout into a new person who can take our place and
start anew, without our fatigue. Yet there are those who, upon
finding that the net no longer holds beneath their feet, try to walk
upon the abyss below instead of allowing themselves to vanish into
it. These are the sad souls we call wraiths; their existence proves
the glorious truth of humanity's infinite power, yet their afterlives
are dominated by a fundamental flaw that makes them tragic.

As I have said before, people do in fact need people, whether they
are "lucky" in the Streisandian sense or not. The proof of this
comes when we examine the dual personality that nearly all wraiths
seem to develop. Each wraith's identity fractures into two facets
upon death (or, possibly, upon the removal of the "caul" which both
shields and shackles the newly-dead; it is possible that this "veil
of death" is a membrane binding the two soul-halves together, and
that those who never tear it away or have it stolen by another wraith
eventually wander their way to Transcendance because of it); the dead
in their own parlance term these segments the Psyche and the Shadow.
The Psyche more closely resembles the person as they were in life,
and this is hardly accidental; the Psyche is the part of the deceased
mind which tries to cling to the life it has left behind, desperately
preserving its identity in the same defiance of Oblivion which life
constitutes, not realizing that its "shift" in this Great Work of
existing has ended and it is free to "go home and sleep". While
there is a tragic nobility to the Psyche, it is also the root of the
wraith's dire condition. The Shadow-self meanwhile represents the
fractures spoken of above, and in turn seeks to widen them; it is the
part of the self which rejects the world as it has rejected the dead,
and seeks to force the Psyche to recognize that it has lost
everything it once treasured, thereby driving the wraith into
Oblivion. The wraiths perceive the Psyche as being "good" and the
Shadow as "evil", but this is inaccurate; when a uniquely wicked
individual (serial killer, dictator, etc.) rises in the Shadowlands,
it is his Psyche which drives him to wreak further havoc, since that
is the identity he has chosen to define himself by, and his Shadow is
trying to force him to give it up and fade away.

Of course, while Euthanatos doctrine indicates that Oblivion is the
fountain of rebirth into which all souls must fall before they can
rise again, observation of the Shadowlands makes it necessary to
question how accurate our beliefs are on this tenet. Perhaps all
wraiths are diseased souls who would be better off consumed by the
Pit, yet perhaps this would not be beneficial after all; the behavior
exhibited by Spectres and the like makes me wonder if this original
function of Oblivon has been corrupted somehow (undoubtedly by the
Nephandi warping the already miserable state of the Shadowlands to
suit their ends), and might now function as a force for destruction
that might not stop at scourging only the Underworld if allowed to
run unchecked. We must study this matter in greater depth.