Catuṣkoṭi

Catuṣkoṭi (Sanskrit; Devanagari: चतुष्कोटि, ) is a logical argument(s) of a 'suite of four discrete functions' or 'an indivisible quaternity' that has multiple applications and has been important in the Dharmic traditions of Indian logic and the Buddhadharma logico-epistemological traditions, particularly those of the Madhyamaka school.
Robinson (1957: pp. 302-303) states (negativism is employed in amplification of the Greek tradition of Philosophical skepticism):
A typical piece of Buddhist dialectical apparatus is the ...(catuskoti). It consists of four members in a relation of exclusive disjunction ("one of, but not more than one of, 'a,' 'b,' 'c,' 'd,' is true"). Buddhist dialecticians, from Gautama onward, have negated each of the alternatives, and thus have negated the entire proposition. As these alternatives were supposedly exhaustive, their exhaustive negation has been termed "pure negation" and has been taken as evidence for the claim that Madhyamika is negativism.Robinson, Richard H. (1957). 'Some Logical Aspects of Nagarjuna's System'. Philosophy East & West. Volume 6, no. 4 (October 1957). University of Hawaii Press. Source: (accessed: Saturday March 21, 2009), pp.302-303 
==Catuṣkoṭi algorithm mapped in partial logical algebra==
The following is an adaptation of the model of Puhakka (2003: p. 133)Puhakka, Kaisa (2003). 'Awakening from the Spell of Reality: Lessons from Nāgārjuna' within: Segall, Seth Robert (2003). Encountering Buddhism: Western Psychology and Buddhist Teachings. Albany, NY, USA: State University of New York Press. ISBN 0-7914-5736-2. Source: (accessed: Tuesday March 24, 2009) with the clear identification of the positive and negative configurations of the Catuṣkoṭi following Ng (1993: pp. 99-105)Ng, Yu-Kwan (1993). T'ien-t'ai Buddhism and Early Madhyamika. Honolulu, HI: University of Hawaii Press, pp.99-105. Where '--' is a sign denoting a grammatical structure or lexical item that negates the proposition in parenthesis.
Where P stands for any proposition and Not-P stands for the diametrical opposite or the contradiction of P (in a relationship of contradistinction): where P and Not-P constitute a complementary bifurcation of mutual exclusivity, collectively constituting an exhaustive set of positions for any given (or determined) propositional array. A propositional array is signified in the model by numerals, traditionally though, propositional arrays were designated 'foot' (Sanskrit: pāda), a lexical item which holds the semantic field: 'line', 'one quartile of śloka'; where 'śloka' (Sanskrit) holds the semantic field: 'verse', 'stanza'.Mukherjee, Sujit (1999). A Dictionary of Indian Literature: Beginnings - 1850. Orient Blackswan, ISBN 8125014535, p.271
Śūnyatā is the ninth 'view' (Sanskrit: dṛṣṭi), the viewless view, a superposition of the eight possible arrays of proposition P [and its 'inseparable contradistinction' (Sanskrit: apoha)].
	Positive configuration
#P
#Not-P
#Both P & Not-P
#Neither P Nor Not-P	
:        
:        
:        
:        		Negative configuration 
#-- (P)
#-- (Not-P)
#-- (Both P & Not-P)
#-- (Neither P Nor Not-P)
The eight arrays or octaves of the iconographic Dharmacakra represent drishti or traditional views that Shakyamuni countered. These eight arrays may be plotted as coordinates on a multidimensional field which may be rendered as a sphere, a mandala, a multidimensional shunya or zero where shunyata denotes zero-ness. The eight arrays are in a concordant relationship where they each constitute a chord to the sphere. The coordinates are equidistant from the epicentre of shunya where the array of the positive configuration (or hemisphere) and the array of the negative configuration (or hemisphere) constitute two polar radii or diametrical complements, a diameter in sum. These are the 'eight limits' (Wylie: mtha' brgyad; Sanskrit: aṣṭānta) of 'openness' (Sanskrit: śūnyatā),Dorje, Jikdrel Yeshe (Dudjom Rinpoche, author), & translated and edited: Gyurme Dorje and Matthew Kapstein (1991). The Nyingma School of Tibetan Buddhism: Its Fundamentals and History. Boston, USA: Wisdom Publications. ISBN 0-86171-199-9, p.158 where śūnyatā is amplified by 'freedom from constructs' or 'simplicity' (Wylie: spros bral; Sanskrit: aprapañca).Dharma Dictionary (June, 2006). 'spros bral'. Source: (accessed: Tuesday March 24, 2009)Abhayadatta (author); Dowman, Keith (translator); Downs, Hugh R. (1985). Masters of Mahāmudrā (Sanskrit: Caturaśītisiddha-pravṛtti ). SUNY Press. ISBN 0887061583, 9780887061585. Source: (accessed: Tuesday March 24, 2009), p.397 Karmay (1988: p. 118) conveys that 'spros bral' is a homologue of 'thig le' (Sanskrit: bindu), where 'spros bral' is literally "without amplification", understood as "that which cannot be displayed".Karmay, Samten Gyaltsen (1988). The Great Perfection (rDzogs Chen): A Philosophical and Meditative Teaching of Tibetan Buddhism. Illustrated Edition. Brill. ISBN 9004087923. Source: (accessed: Tuesday March 24, 2009), p.118
==Exegesis==
Puhakka (2003: p. 134-145) charts the stylized reification process of a human sentient being, the spell of reality'Reality' in this context is not the Dharmakaya, but Maya, a common cultural meme within Dharmic Traditions. Refer: Reality in Buddhism., a spell dispelled by the Catuṣkoṭi: 
We are typically not aware of ourselves as taking something (P) as real. Rather, its reality "takes us," or already has us in its spell as soon as we become aware of its identity (P). Furthermore, it's impossible to take something (P) to be real without, at least momentarily, ignoring or denying that which it is not (not-P). Thus the act of taking something as real necessarily involves some degree of unconsciousness or lack of awareness. This is true even in the simple act of perception when we see a figure that we become aware of as "something." As the German gestalt psychologists demonstrated, for each figure perceived, there is a background of which we remain relatively unaware. We can extend this to texts or spoken communications. For every text we understand there is a context we are not fully cognizant of. Thus, with every figure noticed or reality affirmed, there is, inevitably, unawareness. Is this how a spell works? It takes us unawares.Puhakka, Kaisa (2003). 'Awakening from the Spell of Reality: Lessons from Nāgārjuna' within: Segall, Seth Robert (2003). Encountering Buddhism: Western Psychology and Buddhist Teachings. Albany, NY, USA: State University of New York Press. ISBN 0-7914-5736-2. Source: (accessed: Tuesday March 24, 2009), p.134-135
==Nomenclature, orthography and etymology==
The Catuṣkoṭi in Western Discourse has often been glossed, Tetralemma, which is the nomenclature for the Greek form. Both of the variations have similarities but also differences and the traditions were mutually iterating.
==Antecedents and pervasion==
Antecedents of the Catuṣkoṭi have been charted to grammatical structures in the Vedas. The Nasadiya Sukta of the Rigveda (RV 10.129) contains ontological speculation in terms of various logical divisions that were later recast formally as the four circles of catuskoti: "A", "not A", "A and not A", and "not A and not not A".S. Kak (2004). The Architecture of Knowledge. CSC, Delhi. 
McEvilley (2002: p. 495) maps an interesting case for mutual iteration and pervasion between Pyrrhonism and Madhyamika:
An extraordinary similarity, that has long been noticed, between Pyrrhonism and Mādhyamika is the formula known in connection with Buddhism as the fourfold negation (catuṣkoṭi) and which in Pyrrhonic form might be called the fourfold indeterminacy., p.495
===Gorgias===
Gorgias (c 487-376 BCE), the author of a lost work: 'On Nature or the Non-Existent'.
===Syādvāda===
Jaina Dharma has a sevenfold logical architecture, the Syādvāda, which is a formulation to convey the insight of Anekantavada.
===Brahmajala Sutta: The Supreme Net (What the Teaching Is Not)===
Śākyamuni, as remembered by Ānanda and codified in the Brahmajala Sutta 2.27, when expounding the sixteenth wrong view, or the fourth wrong view of the 'Eel-Wrigglers' (Pali: amarā-vikheppikā), the non-committal equivocators, though the grammatical structure is identical to the Catuṣkoṭi (and there are numerous other analogues of this fourfold grammatical structure within this Sutta), the intentionality of the architecture employed by Nagarjuna is not evident, as rendered into English by Walshe (1987, 1995: p. 81):
'What is the fourth way? Here, an ascetic or Brahmin is dull and stupid. Because of his dullness and stupidity, when he is questioned he resorts to evasive statements and wriggles like an eel: "If you ask me whether there is another world. But I don't say so. And I don't say otherwise. And I don't say it is not, and I don't not say it is not." "Is there no other world?..." "Is there both another world and no other world?..."Is there neither another world nor no other world?..." "Are there spontaneously-born beings?..." "Are there not...?" "Both...? "Neither...?" "Does the Tathagata exist after death? Does he not exist after death? Does he both exist and not exist after death? Does he neither exist nor not exist after death?..." "If I thought so, I would say so...I don't say so...I don't say it is not." This is the fourth case.'Walshe, Maurice (1987, 1995). The Long Discourses of the Buddha: A Translation of the Digha Nikaya. Boston: Wisdom Publications. ISBN 0-86171-103-3, p.81
===Literature review===
Robinson (1957: p. 294)Robinson, Richard H. (1957). 'Some Logical Aspects of Nagarjuna's System'. Philosophy East & West. Volume 6, no. 4 (October 1957). University of Hawaii Press. Source: (accessed: Saturday March 21, 2009) holds that Stcherbatsky (1927)Stcherbatsky, Th. (1927). The Conception of Buddhist Nirvana. Leningrad: Publishing Office of the Academy of Sciences of the USSR., opened a productive period in Madhyamaka studies. Schayer (1933)Schayer, Stanislaw (1933). "Altindische Antizipationen der Aussagenlogik." Bulletin international de l'Academie Polonaise des Sciences et philologie, 1933, pp. 99-96. made a departure into the rules of inference employed by early Buddhist dialecticians and examines the Catuskoti (Tetralemma) as an attribute of propositional logic and critiques Stcherbatsky. Robinson (1957: p. 294) states that "Schayers criticisms of Stcherbatsky are incisive and just." Murti (1955)Murti, T. R. V., 1955. The Central Philosophy of Buddhism. George Allen and Unwin, London. 2nd edition: 1960. makes no mention of the logical contribution of Schayer. According to Robinson (1957: p. 294), Murti furthered the work of Stcherbatsky amongst others, and brought what Robinson terms "the metaphysical phase of investigation" to its apogee though qualifies this with: "Murti has a lot to say about 'dialectic,' but practically nothing to say about formal logic." Robinson (1957: p. 294) opines that Nakamura (1954)Nakamura, Hajime (1954). "Kukao no kigo-ronrigaku-teki ketsumei, (English: 'Some Clarifications of the Concept of Voidness from the Standpoint of Symbolic Logic')" Indogaku-bukkyogaku Kenkyu, No. 5, Sept., 1954, pp. 219-231., developed Schayer's methodology and defended and progressed its application.
Robinson (1957: p. 293) opines that the 'metaphysical approach' evident foremost in Murti (1955) was not founded in a firm understanding of the 'logical structure of the system', i.e. catuskoti, for example:
Several fundamental limitations of the metaphysical approach are now apparent. It has tried to find comprehensive answers without knowing the answers to the more restricted questions involved - such questions as those of the epistemological and logical structure of the system.Robinson, Richard H. (1957). 'Some Logical Aspects of Nagarjuna's System'. Philosophy East & West. Volume 6, no. 4 (October 1957). University of Hawaii Press. Source: (accessed: Saturday March 21, 2009), p,293
Robinson (1957: p. 296) conveys his focus and states his methodology, clearly identifying the limitations in scope of this particular publication, which he testifies is principally built upon, though divergent from, the work of Nakamura:
In considering the formal structure of Nagarjuna's argumentation, I exclude epistemology, psychology, and ontology from consideration.... Such extra-logical observations as emerge will be confined to the concluding paragraphs...Robinson, Richard H. (1957). 'Some Logical Aspects of Nagarjuna's System'. Philosophy East & West. Volume 6, no. 4 (October 1957). University of Hawaii Press. Source: (accessed: Saturday March 21, 2009), p.296
==Nargarjuna==
The Catuṣkoṭi was employed particularly by Nagarjuna who developed it and engaged it as a 'learning, investigative, meditative'Rendering of the Three prajnas. portal to realize the 'openness' (Sanskrit: Śūnyatā), of Shakyamuni's Second Turning of the Dharmacakra, as categorized by the Sandhinirmocana Sutra.
Robinson (1957: p. 294), building on the foundations of Liebenthal (1948)Liebenthal, Walter (1948). The Book of Chao. Peking: Gatholic University Press of Peking, 1948, p.3O. to whom he gives credit, states:
What Nagarjuna wishes to prove is the irrationality of Existence, or the falsehood of reasoning which is built upon the logical principle that A equals A.... Because two answers, assertion and denial, are always possible to a given question, his arguments contain two refutations, one denying the presence, one the absence of the probandum. This double refutation is called the Middle Path. [emphasis evident in Robinson]Robinson, Richard H. (1957). 'Some Logical Aspects of Nagarjuna's System'. Philosophy East & West. Volume 6, no. 4 (October 1957). University of Hawaii Press. Source: (accessed: Saturday March 21, 2009), p.294
==Catuṣkoṭi post-Nargarjuna==
The Catuṣkoṭi, following Nagarjuna, has had a profound impact upon the development of Buddhist logic and its dialectical refinement of Tibetan Buddhism. 
Robinson (1957: p. 294) qualifies the import of Nagarjuna's work (which includes Nagarjuna's application of the Catuskoti) due to the embedded noise in the scholarly lineage: "Certainly some of Nagarjuna's ancient opponents were just as confused as his modern interpreters...". This noise may also have co-arisen with Nagarjuna, following the work of Jayatilleke (1967).
==Catuṣkoṭi paradox: a simple complex==
Wayman (1977) proffers that the Catuṣkoṭi may be employed in different ways and often these are not clearly stated in discussion nor the tradition. Wayman (1977) holds that the Catuṣkoṭi may be applied in suite, that is all are applicable to a given topic forming a paradoxical matrix; or they may be applied like trains running on tracks (or employing another metaphor, four mercury switches where only certain functions or switches are employed at particular times). This difference in particular establishes a distinction with the Greek tradition of the Tetralemma. Also, predicate logic has been applied to the Dharmic Tradition, and though this in some quarters has established interesting correlates and extension of the logico-mathematical traditions of the Greeks, it has also obscured the logico-grammatical traditions of the Dharmic Traditions of Catuṣkoṭi within modern English discourse.
==Four Extremes==
The 'Four Extremes' (; Sanskrit: caturanta; Devanagari: चतुरन्त) Dorje, Jikdrel Yeshe (Dudjom Rinpoche, author), & translated and edited: Gyurme Dorje and Matthew Kapstein (1991). The Nyingma School of Tibetan Buddhism: Its Fundamentals and History. Boston, USA: Wisdom Publications. ISBN 0-86171-199-9, p.129 Enumerations. is a particular application of the Catuṣkoṭi:
*Being (Wylie: yod)
*Non-being (Wylie: med)
*Both being and non-being (Wylie: yod-med)
*Neither being and non-being (Wylie: yod-med min)
Dumoulin et al. (1988, 2005: pp. 43-44), in the initially groundbreaking work on Zen which is now for the most part dated due to progress in scholarship (though still useful as the premier English work of comprehensive overview), model a particular formulation of the Catuṣkoṭi that approaches the Caturanta engaging the Buddhist technical term 'dharmas' and attribute the model to Nagarjuna:
If we focus on the doctrinal agreement that exists between the Wisdom Sūtras'Wisdom Sūtras' is a gloss of Prajñāpāramitā Sūtras. and the tracts of the Mādhyamika we note that both schools characteristically practice a didactic negation. By setting up a series of self-contradictory oppositions, Nāgārjuna disproves all conceivable statements, which can be reduced to these four:
:All things (dharmas) exist: affirmation of being, negation of nonbeing
:All things (dharmas) do not exist: affirmation of nonbeing, negation of being
:All things (dharmas) both exist and do not exist: both affirmation and negation
:All things (dharmas) neither exist nor do not exist: neither affirmation nor negation 
With the aid of these four alternatives (catuṣkoṭika: affirmation, negation, double affirmation, double negation), Nāgārjuna rejects all firm standpoints and traces a middle path between being and nonbeing. Most likely the eight negations, arranged in couplets in Chinese, can be traced back to Nāgārjuna: neither destruction nor production, neither annihilation nor permanence, neither unity nor difference, neither coming nor going.Dumoulin, Heinrich (author); Heisig, James W. (translator); Knitter, Paul (translator); with introduction by McCrae, John (1988, 2005). Zen Buddhism: A History; Volume 1 India and China. Bloomington, Indiana, USA: World Wisdom, Inc. ISBN 0-941532-89-5, pp.43-44
===Alternate Four Limits/Four Extremes===
A Mantrayana enumeration of the Four Limits or the Four Extremes within the Buddhadharma is also common. These four 'limits' are evident in the earliest sutras of the Theravadin of the First Turning, through the Second Turning philosophy of Nagarjuna and his disciples and commentators and also evident in the Third Turning as evidenced in the presentation of Padmasambhava. Padmasambhava in his 'Secret Instruction in a Garland of Vision' lists them as follows with the English rendering following Dowman (2003)Dowman, Keith (2003, revised). The Flight of the Garuda: the Dzogchen Tradition of Tibetan Buddhism. Somerville, MA, USA: Wisdom Publications. ISBN 0861713672, p.146 and Wylie following Norbu et. al. (2001)Norbu, Namkhai (2001). The Precious Vase: Instructions on the Base of Santi Maha Sangha. Shang Shung Edizioni. Second revised edition. p. 103. (Translated from the Tibetan, edited and annotated by Adriano Clemente with the help of the author. Translated from Italian into English by Andy Lukianowicz.). This is a restricted text. :
*the Hedonist' or 'Chalpas' : does not perceive, ascribe to the view or realize that all events, dharmas, etc. have a cause and an effect;
*the 'Atheist' or 'Gyangphenpas' : unable to see or perceive past and future lives, the atheist toils for wealth and power in this lifetime alone. They engage in intrigue;
*the 'Nihilist' or 'Murthugpas' : holds that there is no causality or causal relationship between events and dharmas. They are of the view that everything is adventitiously arisen due to chance and events and that dharmas dissipate and vanish into the void. Death is the ultimate cessation and there is no continuity between lives; and
*the Eternalist' or 'Mutegpas' : holds to the view of an eternal, unchanging 'atman', where atman is often rendered as 'soul' in English. There is considerable diversity of the mechanics of causality with proponents of this view. Some perceive the atman as having a cause but not effect, an effect but no cause, or indeed a complex causality or causal relationship.
Each one of these extreme views, limits and binds the open, unbounded spaciousness of the natural mind.
===Lexicon: technical language and terminology===
Within English Buddhist logico-epistemological discourse, there is and has been historically, much obstruction to an understanding of the Caturanta (as the Catuṣkoṭi) due to inherent negligence in terminology not being clearly defined from the outset. That said, acquisition of terminology must be engaged and actualized though the sadhana of the 'mūla prajñā', as definitions are slippery and challenging to pinpoint that hold for all contexts. Language usage in Buddhist logic is not intuitive but technical and must be learnt, acquired through the perfection and power of 'diligence' (Sanskrit: vīrya). The following quotations are cited to provide insight (in lieu of technical definitions) into the understanding of the technical Buddhist terms 'existence', 'nature', 'being', 'entity' and 'svabhava' which are all mutually qualifying.
Robinson (1957: p. 297) renders Mūlamadhyamakakārikā 21.14, thus:
"He who posits an entity becomes entangled in eternalism and annihilism,
since that entity has to be either permanent or impermanent."Robinson, Richard H. (1957). 'Some Logical Aspects of Nagarjuna's System'. Philosophy East & West. Volume 6, no. 4 (October 1957). University of Hawaii Press. Source: (accessed: Saturday March 21, 2009), p.297
Robinson (1957: p. 300) in discussing the Buddhist logic of Nagarjuna, frames a view of 'svabhava':
Svabhava is by defini[t]ion the subject of contradictory ascriptions. If it exists, it must belong to an existent entity, which means that it must be conditioned, dependent on other entities, and possessed of causes. But a svabhava is by definition unconditioned, not dependent on other entities, and not caused. Thus the existence of a svabhava is impossible. [NB: typographical errors repaired] Robinson, Richard H. (1957). 'Some Logical Aspects of Nagarjuna's System'. Philosophy East & West. Volume 6, no. 4 (October 1957). University of Hawaii Press. Source: (accessed: Saturday March 21, 2009), p.300
"Nature" (a gloss of prakrti which in this context equals svabhava) does not entail an alter-entity:
The term "nature" (prakrti equals svabhava) has no complement..."If (anythings) existence is due to its nature, its non-existence will not occur, since the alter-entity (complement) of a nature never occurs." (Mūlamadhyamakakārikā, 15.8)
That is, a nature is the class of properties attributed to a class of terms Since they are necessarily present throughout the range of the subject or class of subjects, cases of their absence do not occur.
Karunadasa (1999, 2000: p. 1) holds that Early Buddhism and early Buddhist discourse "often refer to the mutual opposition between two views": 
*'permanence' or 'eternalism' (Pali: sassatavada) also sometimes referred to as 'the belief in being' (Pali: bhava-ditti); and 
*'annihilation' or 'nihilism' (Pali: ucchadevada) also sometimes referred to as 'the belief in non-being' (Pali: vibhava-ditti).Karunadasa, Y. (1999, 2000). "The Buddhist Critique of Sassatavada and Ucchedavada: The Key to a proper Understanding of the Origin and the Doctrines of early Buddhism." from: Karunadasa, Y. (1999, 2000). The Middle Way, U.K., vol. 74 & 75.
As Shakyamuni relates in a 'thread' (Sanskrit: sūtra) of discourse to Kaccānagotta in the Kaccānagotta Sutta, rendered into English by Myanmar Piṭaka Association Editorial Committee (1993: p. 35):
"For the most part, Kaccāna, sentient beings depend on two kinds of belief - belief that 'there is' (things exist) and belief that 'there is not' (things do not exist).Myanmar Piṭaka Association Editorial Committee (1993). Nidāna Saṃyutta: Group of Related Discourses on Causal Factors from Nidānavagga Saṃyutta: Division Containing Groups of Discourses on Causal Factors. Shakti Nagar, Delhi, India: Sri Satguru Publications. ISBN 81-7030-367-2. p.35
Karunadasa (1999, 2000: p. 1) states that:
...it is within the framework of the Buddhist critique of sassatavada and ucchadavada that the Buddhist doctrines seem to assume their significance. For it is through the demolition of these two world-views that Buddhism seeks to construct its own world-view. The conclusion is that it was as a critical response to the mutual opposition between these two views that Buddhism emerged as a new faith amidst many other faiths.
==Notes==
==See also==
* Nagarjuna
* Paraconsistent logic
* Prasangika
* Two-truths doctrine
==References==
*Jayatilleke, K.N. (1967). 'The Logic of Four Alternatives'. Philosophy East and West. Vol.17:1–4. Hawai'i, USA: University of Hawai'i Press.
*Wayman, Alex (1977). 'Who Understands the Four Alternatives of the Buddhist Texts?'. Philosophy East and West. Vol.27: no.1, Jan., 1977. Hawai'i, USA: University of Hawai'i Press.
*Matilal, Bimal Krishna (1971). Epistemology, Logic, and Grammar in Indian Philosophical Analysis. Paris: Mouton.
*Westerhoff, J. (2006) 'Nagarjuna's catuskoti.' , Journal of Indian philosophy., 34 (4), pp. 367-395.
*Ruegg, D. Seyfort (1977). 'The uses of the four positions of the Catuskoti and the problem of the description of reality in Mahāyāna Buddhism'. Journal of Indian Philosophy. Volume 5, Numbers 1-2 / September.
*http://books.google.com.au/books?id=JqLa4xWot-YC&pg=PA74&lpg=PA74&dq=catuskoti&source=bl&ots=plHIG_dLsh&sig=5OEWoVtDzl_f57bWqip6bbGlVxw&hl=en&ei=a0zHSdDmI4yGkAWZ44nDDA&sa=X&oi=book_result&resnum=2&ct=result
*http://books.google.com.au/books?id=NlmPNhzar5YC&pg=PA132&lpg=PA132&dq=catuskoti&source=bl&ots=pf57WME2YC&sig=9D_IDCrllXqOeguBr9Nd_xzKtEU&hl=en&ei=a0zHSdDmI4yGkAWZ44nDDA&sa=X&oi=book_result&resnum=8&ct=result
*www.smith.edu/philosophy/documents/MountainsareJustMountains.pdf
*Gunaratne, R. D. (1986). 'Understanding Naagaarjuna's Catuskoti.' Philosophy East & West. V. 36 No. 3 (July 1986). University of Hawaii Press, pp. 213-234
*http://www.scribd.com/doc/6567025/dignaganvayavyatireka
*object of negation, object of refutation
*Vidhabhusana, Satis Chandra (1907). History of the Mediaeval School of Indian Logic. Calcutta University.
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