  Landauer's principle is, roughly, the principle that there is an entropic
cost associated with implementation of logically irreversible operations.
Though widely accepted in the literature on the thermodynamics of computation,
it has been the subject of considerable dispute in the philosophical
literature. Both the cogency of proofs of the principle and its relevance,
should it be true, have been questioned. In particular, it has been argued that
microscale fluctuations entail dissipation that always greatly exceeds the
Landauer bound. In this article Landauer's principle is treated within
statistical mechanics, and a proof is given that neither relies on neglect of
fluctuations nor assumes the availability of thermodynamically reversible
processes. In addition, it is argued that microscale fluctuations are no
obstacle to approximating thermodynamic reversibility as closely as one would
like
