 Many proponents of orthodox quantum theory believe that decoherence somehow resolves the measurement problem itself. It is not easy to understand this belief. In the first formulation of the measurement problem, nothing prevents us from including in the apparatus all sources of decoherence. But then decoherence can no longer be in any way relevant to the argument. Be that as it may, Bohm (1952) gave one of the best descriptions of the mechanisms of decoherence, though he did not use the word itself. He recognized its importance several decades before it became fashionable. (See also the encyclopedia entry on  The Role of Decoherence in Quantum Mechanics.)