  It is argued by Duff that only the time variation of dimensionless constants
of nature is a legitimate subject of enquiry, and that dimensional constants
such as c, h-bar and G... are merely human constructs whose value has no
operational meaning. We refute this claim and point out that such varying
dimensional "constants" can have significant physical consequences for the
universe that can be directly measured in experiments. Postulating that
dimensional constants vary in time can significantly change the laws of
physics.
