An important concept in statistical mechanics is what physicist Leonard Suskind calls the "conservation of distinctions".  This means that if one knows the current state of the system, then one also know here the system is going, and equally importantly, one knows where the system came from. The system in its current state has memory of it's past state.

A process that has multiple states going to a single current state loses this distinction and one no longers knows its prior state.  Information in memory is lost.  See Professor Suskind's First lecture on Statistical mechanics for more details under the following license.

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