  If the human race comes to an end relatively shortly, then we have been born
at a fairly typical time in history of humanity. On the other hand, if humanity
lasts for much longer and trillions of people eventually exist, then we have
been born in the first surprisingly tiny fraction of all people. According to
the Doomsday Argument of Carter, Leslie, Gott, and Nielsen, this means that the
chance of a disaster which would obliterate humanity is much larger than
usually thought. Here I argue that treating possible observers in the same way
as those who actually exist avoids this conclusion. Under this treatment, it is
more likely to exist at all in a race which is long-lived, as originally
discussed by Dieks, and this cancels the Doomsday Argument, so that the chance
of a disaster is only what one would ordinarily estimate. Treating possible and
actual observers alike also allows sensible anthropic predictions from quantum
cosmology, which would otherwise depend on one's interpretation of quantum
mechanics.
