The Collaborative International Dictionary of English v.0.48:

Manichaeism \Man"i*chae*ism\, Manicheism \Man"i*che*ism\, n.
   [Cf. F. manich['e]isme.]
   The doctrines taught, or system of principles maintained, by
   the Manichaeans.
   [1913 Webster]

The Devil's Dictionary (1881-1906):

MANICHEISM, n.  The ancient Persian doctrine of an incessant warfare
between Good and Evil.  When Good gave up the fight the Persians
joined the victorious Opposition.