Heuristic or heuretic, or "ars inveniendi" was the 
name of a certain branch of study, not very clearly circumscribed,
belonging to logic, or to philosophy, or to
psychology, often outlined, seldom presented in detail,
and as good as forgotten today.  The aim of heuristic is to
study the methods and rules of discovery and invention.
A few traces of such study may be found in the he commentators
of Euclid; a passage of PAPPUS is particularity
interesting in this respect. The most famous attempts 
to build up a system of heuristic are due to Descartes and
to LIEBNITZ, both great mathematicians and philosophers.
Bernard BOLZANO presented a notable detailed account of
heuristic.  The present booklet is an attempt to revive
heuristic in a modern and modest form. See MODERN HEURISTIC.
     Heuristic, as an adjective, means "serving to discover"