Decipiency

from The Collaborative International Dictionary of English v.0.48

Decipiency \De*cip"i*en*cy\, n. [L. decipiens, p. pr. of
   decipere. See {Deceive}.]
   State of being deceived; hallucination. [Obs.] --Sir T.
   Browne.
   [1913 Webster]