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Medieaval Indian
Logic: Dignaga

The Indian Buddhist philosopher and logician Dignaga (A.D. 480540), a disciple of Vasubandhu,
laid the foundations for the Buddhist teachings on cognition theory and logic. Dignaga's Pramanasamuccaya
(Compendium of the Means of True Knowledge) is one of the greatest works on Buddhist logic.



Indian logic
can be traced back to some centuries B.C. It seems to
have developed independently from Greek logic, even if there are similarities and
parallels. Ancient Indian logic was born in the context of debate on religious and
philosophical matters. In the mediaeval period from about the 4th century on, logic
evolved in dealing with problems of valid knowledge, i.e. perception and inference



The formal content of Trairupya doctrine, Dignaga’s Hetucakra, and Uddyotakara’s extension[PDF], 297 kB
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In the present article, we will take a fresh look onto the doctrine of Trairupya
and its connection to Dignaga’s Hetucakra and Uddyotakara’s extension of Dignaga’s ideas.
We try to utilize formulas as little as possible by concentrating instead on formal
methods (tables, illustrations) which could – but must not  be translated into formulas.
For sake of completeness, we will also employ the standard predicate logical formulation and
compare it to the results given by the other strategies.
Acknowledgement
This paper has been written during my stay as a Numata Scholar at Ryokoku University, Kyoto (Japan). I thank Prof. Katsura, Kyoto, for inviting me, for encouraging me to pursue this research and for discussions on the subject of this paper. I thank also Dr. Okazaki, Hiroshima, for our extensive correspondence on the subject of Indian logic, for his many valuable hints concerning the philological background, and for his critical reading of different versions of this paper.

Problems of transcribing avinaabhaava into predicate logic[PDF], 91 k
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Translating ancient logical texts into modern symbolic logic can
be a valuable method of getting access to an otherwise
incomprehensible train of thought. Representing a definition or an argument in
symbolic form, carries the risk of severely twisting the
underlying ideas. Thus the use of modern symbolic logic is often
of doubtful value for interpretational purposes.

Stanislaw Schayer's Research on Nyaaya. Journal of Indian Philosophy 32: 295319,2004[PDF]
96 k
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Nyaaya
denotes the oldest Indian logic.
One main topic of Nyaaya is the fivemembered scheme which, since its discovery in the West,
has often been compared to Aristotelian syllogistic.
St. Schayer was the first Western Indologist who used modern
Predicate Logic for formulating the "Indian syllogism" in
symbolic outfit. In this paper we discuss in detail the
problematic parts of such a formalization of an ancient
logic.

Using Formulas for the Interpretationof Ancient Indian Logic [PDF], 91 k
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Utilising western logical concepts and formalisms in a naive manner for the
research on ancient Indian logic is not without risks. There are some
inbuilt limitations of modern formal logic which prevent it from being
the "natural universal instrument" for the understanding of each and every logical system.

Das Rad der Gründe [PDF]
612 k (German language)
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Dignaga's
hetucakra (The wheel of reason) was his first work on formal logic.
It may be regarded as a bridge between the older doctrine of trairuupia and Dignaga's own later theory of vyaapti
which is a concept related to the Western notion of implication.

