to show that their systems were taught in the Upani@sads, and thus
wrote commentaries thereon to prove their interpretations, and also wrote
commentaries on the _Brahmasûtra_, the classical exposition of the
philosophy of the Upani@sads. In addition to the works of these Vai@s@nava
thinkers there sprang up another class of theistic works which were of a
more eclectic nature. These also had their beginnings in periods as old
as the Upani@sads. They are known as the S'aiva and Tantra thought, and are
dealt with in the second volume of this work.

We thus see that the earliest beginnings of most systems of Hindu thought
can be traced to some time between 600 B.C. to 100 or 200 B.C. It is
extremely difficult to say anything about the relative priority of the
systems with any degree of certainty. Some conjectural attempts have
been made in this work with regard to some of the systems, but how far
they are correct, it will be for our readers to judge. Moreover during
the earliest manifestation of a system some crude outlines only are
traceable. As time went on the systems of thought began to develop
side by side. Most of them were taught from the time in which they
were first conceived to about the seventeenth century A.D. in an
unbroken chain of teachers and pupils. Even now each system of
Hindu thought has its own adherents, though few people now

9

care to write any new works upon them. In the history of the growth of
any system of Hindu thought we find that as time went on, and as new
problems were suggested, each system tried to answer them consistently
with its own doctrines. The order in which we have taken the
philosophical systems could not be strictly a chronological one. Thus
though it is possible that the earliest speculations of some form of