The histories approach assumes that the same fundamental quantum mechanical laws apply to systems of any size, from quarks to jaguars to quasars. Classical mechanics is a very good approximation to the more exact quantum laws in appropriate circumstances. The following remarks  provide only a broad outline of how the classical world emerges from quantum theory; see the   Further Reading supplement for additional material. Gell-Mann &amp; Hartle (1993, 2007) and Hartle (2011), and are broadly consistent with those of Omn&egrave;s (1999). They are discussed at somewhat greater length in Ch. 26 of Griffiths (2002a).--> 