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PREFACE
An important point in the external history of Indian Philosophy which still remains unexplained to a great extent is the relationship between the various systems and schools. This may be due in part to the tradition of the texts the insufficiency of which does not allow us to see more clearly. Nevertheless it is striking how often important ideas and even whole systems are not being noticed beyond the limits of the own school.
Looking at things in general we may say that we encounter constructive discussion with opponent theories especially when there were different opinions on a certain subject, as for example on the problem of generality (sāmānyam) as the object of verbal cognition, or on the details of the act of cognition in the case of perception. Yet these are cases where the interest is concerned less with the opponent's theory as such but rather with the elucidation and defence of the own theory by discussing it with the opponent.
The discussion moves farther in the opponent's field if the topic is one of the fundamental theories of the other system. Of such kind are in the discussion with the Buddhists, for instance, the argument about the existence or non-existence of a soul, or with the Nyāya the problem of the existence of a supreme god. Very seldom the heterogeneous system is considered in its totality and if it happens the rendering of this system is usually not more than a rough
