  It has been argued [T. Rudolph and B.C. Sanders, Phys. Rev. Lett. {\bf 87},
077903 (2001)] that continuous-variable quantum teleportation at optical
frequencies has not been achieved because the source used (a laser) was not
`truly coherent'. Van Enk, and Fuchs [Phys. Rev. Lett, {\bf 88}, 027902
(2002)], while arguing against Rudolph and Sanders, also accept that an
`absolute phase' is achievable, even if it has not been achieved yet. I will
argue to the contrary that `true coherence' or `absolute phase' is always
illusory, as the concept of absolute time on a scale beyond direct human
experience is meaningless. All we can ever do is to use an agreed time
standard. In this context, a laser beam is fundamentally as good a `clock' as
any other. I explain in detail why this claim is true, and defend my argument
against various objections. In the process I discuss super-selection rules,
quantum channels, and the ultimate limits to the performance of a laser as a
clock. For this last topic I use some earlier work by myself [Phys. Rev. A {\bf
60}, 4083 (1999)] and Berry and myself [Phys. Rev. A {\bf 65}, 043803 (2002)]
to show that a Heisenberg-limited laser with a mean photon number $\mu$ can
synchronize $M$ independent clocks each with a mean-square error of
$\sqrt{M}/4\mu$ radians$^2$.
