A person's qualifications, although important, are not the only thing
to consider. The ultimate authority for arguments about the world
is the world itself. If the argument is logical and is based on
reliable real-world data (for example, if it contains verifiable data
or has reliable references), then the argument has authority regardless
of who is giving it.
Qualifications consist of a lot more than letters after one's name.
Perhaps the most important quality is how the person is regarded by
others in the field. The soundness of the person's past work is
another important consideration.
One must also consider the qualifications of others who approve or
disapprove of the argument. When an argument withstands peer review,
the authority of those who review it adds to the authority of the
original author. Withstanding further exposure adds even more to the
argument's reliability.
This argument about qualifications, if applied uniformly, would sink
creationism in a second. For every creationist who claims one thing,
there are dozens of scientists (probably more), all with far greater
professional qualifications, who say the opposite.
