  Entropy in thermodynamics is an extensive quantity, whereas standard methods
in statistical mechanics give rise to a non-extensive expression for the
entropy. This discrepancy is often seen as a sign that basic formulas of
statistical mechanics should be revised, either on the basis of quantum
mechanics or on the basis of general and fundamental considerations about the
(in)distinguishability of particles. In this article we argue against this
response. We show that both the extensive thermodynamic and the non-extensive
statistical entropy are perfectly alright within their own fields of
application. Changes in the statistical formulas that remove the discrepancy
must be seen as motivated by pragmatic reasons (conventions) rather than as
justified by basic arguments about particle statistics.
