explanatory hypothesis of that phenomenon.  Its form
　　   is not truth-functional nor are the relationships of
　　   that premises completely rulegoverned.  Peirce said,
　　   "It must be remembered  that  retroduction, although
　　   hampered very little by logical rules, nevertheless,
　　   is logical inference, asserting its conclusion  only
　　   problematically or conjecturally...."(7)

　　　　  Retroduction  does have a recognizable  pattern,
　　   and indeed  it is very  close  to the three-membered
　　   syllogism  of Indian logic.  Its form,  according to
　　   Peirce, is:

　　　　  12. The surprizing fact Q is observed.

　　　　  13.  But  if P were true, Q would be a matter of
　　　　　　 course.

　　　　  14. Hence, there is reason to suspect  that P is
　　　　　　 true.

　　   As a schema, for retroduction we have:

　　　　  (12') q
　　　　  (13') q because p
　　　　  (14')p

　　   which  is isomorphic  with that of the Nyaaya  (that
　　   is, pak.sa, because  hetu  and  d.r.s.taanta;  hence
　　   there  is evidence  for the pak.sa).  The similarity
　　   (sapak.sa) and dissimilarity  (vipak.sa) cases serve
　　   as further  evidence  in support  of the explanatory
　　   justification.

　　　　  The  philosopher  of  science,  Norwood  Hanson,
　　   argued that retroduction  was a "logic of discovery"
　　   which  led  to  deductive-nomological  explanations.
　　   Like Peirce, Hanson pointed out that the reversal of
　　   a  retroduction  was  a  deductive  inference  'q, q
　　   because p', becomes 'p, if p, then q, hence q'.  The
　　   notion of reversal" or inverting" a retroduction  is
　　   not a technique  or rule of formal logic, but rather
　　   a simple psychological  description  of changing the
　　   order of premises.

　　　　  If the three-membered  syllogism is retroduction
　　   and　　 if   a   retroduction　　 is   part　　 of　　 a
　　   retroductive-deductive  pair, one should  expect  to
　　   find internal evidence  for the presence  or absence
　　   of a deductive fragment. To return to the Nyaaya and
　　   its commentary on this three-membered  syllogism, is
　　   there   internal   evidence   to   treat   it  as  a
　　   retroduction-cum-deduction?  A  crucial   point   of
　　   philological  interpretation  is the function of the
　　   ablative  "because"　　 and  the  meaning  of  "hetu"
　　   itself. The weakness of the standard view is that it