  The Meissner effect is an important characteristic of superconductivity and
is critical to distinguishing superconductivity from simply the absence of
electrical resistance (perfect conductivity). In a recent paper published in
American Journal of Physics, Ess\'en and Fiolhais claimed that the Meissner
effect is explained by classical physics. [Am. J. Phys. {\textbf{80}} 164,
(2012).] We claim it cannot be understood by classical mechanics and point out
that their derivation of the Meissner effect by classical physics is based on
an inadequate treatment of the magnetic field energy. A correct treatment of
the magnetic field energy clarifies the need for quantum mechanics to
understand the Meissner effect. We stress that Meissner effect is energetically
favorable due to the energy of condensation of the Cooper pairs. The
condensation of electrons into Cooper pairs is best understood as a quantum
mechanical phenomenon.
