Ladyman et al (2007) proposed a model of the implementation of
logical operations by physical processes in order to clarify the exact
statement of Landauer's Principle, and then ordered a new proof of the
latter based on the construction of a thermodynamic cycle, arguing
that if Landauer's Principle were false it would be possible to harness
a machine that violated it to produce a violation of the second law
of thermodynamics. In a recent paper in this journal, John Norton
(2011) directly challenges the consistency of that proof. In the present
paper we defend the proof given by Ladyman et al against his critique.
In particular, contrary to what Norton claims, we argue that the pro-
cesses used in the proof cannot be used to construct a cycle that enacts
erasure in a thermodynamically reversible way, and that he does not
show that the processes used in the proof violate the Second Law of
Thermodynamics
