Independence-Friendly Existential Graphs

1. Independence-Friendly Existential Graphs Ahti-Veikko Pietarinen Department of Philosophy University of Helsinki 29 April 2004

2. Outline • Symbolic vs. diagrammatic logic • Independence-friendly (IF) logic • Existential graphs (EG) • IF EGs • Conclusions

3. Symbolic vs. diagrammatic logical representations • 20th century: Mainly symbolic logic • 19th century: Lots of diagrammatic logics (Venn, Kempe, Sylvester, Peirce,…) • Earlier: (Euler, Bruno, Vives,…) • 21st century: ? • Diagrams are not conventional like symbols, but iconic

4. Independence-friendly (IF) logic Jaakko Hintikka: • ”The real source of the expressive power of first-order logic lies not in the notion of quantifier per se, but in the idea of a dependent quantifier” Hintikka, Jaakko (1996: 47): The Principles of Mathematics Revisited, CUP.

5. What is IF logic? • Allow explicit independence between quantifiers: • For all x there exists y ”independently of” x • Skolem functions: not but • Semantic games of imperfect information • Arrays of Skolem functions = winning strategies

6. Henkin quantifiers • Henkin (1959): true in M iff Leon Henkin (1961): ”Some Remarks on Infinitely Long Formulas”, Infinistic Methods. Proceedings of the Symposium on Foundations of Mathematics, Pergamon Press, 167-183.

7. Henkin quantifiers • Krynicki normal forms (1993) reduce to

8. Branching quantifiers • “Some relative of every villager and some friend of every townsman hate each other” (Hintikka 1974) • “Most linguists and most logicians admire each other” (Barwise 1979)

9. Language of IF logic • Let be in the scope of Given wffs of • We may even have and are Sandu, G. & Pietarinen, A.-V. (2001): “Partiality and Games: Propositional Logic”, Logic Journal of the IGPL 9, 107-127.

10. Binding vs. priority scope • Binding scope: The reach of any single instantiation of values • Priority scope: Logical ordering of quantifiers • In FOL these go together, in IF logic not • Limitation of the Frege-Russell concept of logic

11. Game-theoretic semantics • Henkin (1961): “Imagine, for instance, a “game” in which a First Player and a Second Player alternate in choosing an element from a set I; the infinite sequence generated by this alternation of choices then determines the winner” Leon Henkin (1961): ”Some Remarks on Infinitely Long Formulas”, Infinistic Methods. Proceedings of the Symposium on Foundations of Mathematics, Pergamon Press, 167-183.

12. Game-theoretic semantics • Hintikka (1973): a game between • Non-cooperative, finite, zero-sum games • Complete but possibly imperfect information and imperfect recall • FOL, modal logic, dynamic logic,… A.-V. Pietarinen (2004): “Some Games Logic Plays”, Logic, Thought and Action, Kluwer

13. Game-theoretic semantics then chooses then chooses then chooses then chooses then and In IF logic strong game negation, not classical, weak contradictory negation!

14. Game-theoretic semantics • Winning conventions if is a win for if is a win for • Winning strategies is true in iff there exists a winning strategy for in is false in iff there exists a winning strategy for in

15. Imperfect information • In any player chooses “without knowing” previous choices in W • Induces equivalence relations between game histories • Information sets in extensive-form games • Non-determined formulas

16. Extensive-form games • Interactive move-by-move setting • Provides derivational histories • Explicit representation of information flow • Imperfect recall (memory) • Partial semantics A.-V. Pietarinen (2004): “Semantic Games in Logic and Epistemology”, Logic, Epistemology and the Unity of Science, Kluwer Academics.

17. Basic properties of IF logic • Agrees with the -fragment of the second-order logic • Compactness • Downwards Löwenheim-Skolem • Not recursively axiomatisable • Expresses NP-complete properties on finite models

18. Existential Graphs Charles S. Peirce (1839-1914): • ”I do not think I ever reflect in words: I employ visual diagrams, firstly, because this way of thinking is my natural language of self-communion, and secondly, because I am convinced that it is the best system for the purpose” (MS 619:8, 1909)

19. Existential Graphs • Entitative Graphs (1886) → Existential Graphs (EG, 1895) • The goal is not to have “heterogeneous” logic but iconic, diagrammatic, graphical • Origins in algebra of relatives and valental chemistry • EGs “put before us moving-pictures of thought” (1906) A.-V. Pietarinen (2004): ”Peirce’s Magic Lantern I: Moving Pictures of Thought”, Transactions of the C.S. Peirce Society

20. Alpha, Beta, Gamma… • Alpha graphs = propositional logic • Beta graphs ≈ predicate logic /w identity w/o constants, function symbols • Gamma graphs = • Modalities (possibility, necessity, knowledge, time…, “tinctures”, 1908) • Higher-order assertions • “Graphs of graphs”, abstractions • Interrogatives, imperatives, absurdities… • Delta graphs (1911): “…to deal with modals” Don D. Roberts (1973): The Existential Graphs of Charles S. Peirce, Mouton

21. Alpha part • Sheet of Assertion (SA, universe of discourse) • Cuts (negations) • Juxtaposition (conjunction) SA T SA SA SA

22. Alpha part • Conditional (“the scroll”)

23. phoenix Beta part A man eats a man • Rhemas (predicate terms) • Lines of identities (LI, existence, identity, predication, subsumption) phoenix A phoenix doesn’t exist Something exists that is not phoenix thunder lightning If it thunders, it lightens

24. Beta part • Another example, coreference: walks in man park whistles A man walks in the park. He whistles.

25. Beta part • “Binding scope” is given by the system of LIs (ligatures) • “Priority scope” is given by the system of cuts • In FOL these go together, in Beta they do not • Beta not isomorphic to FOL • Rather like dynamic semantics ? ?

26. Beta part • Different readings of “is” not logically different: • Existence Socrates exists • Identity L. Carroll is C. Dodgson • Predication Socrates is mortal • Subsumption Man is an animal • Coreference A man walks in the park. He whistles. A.-V. Pietarinen (2004): Signs of Logic: Peircean Themes on the Philosophy of Language, Games, and Communication, Kluwer

27. Beta part • Rhemas, graphs, inferences are “continuous with one another” (1908) • Connectivity between different parts of SAs by LIs and juxtaposition gives rise to propositions • Meaning-preserving transformations as continuous deformations give rise to inferential arguments • Topological system

28. Gamma part • Modalities (It is possible that it rains) • Higher-order assertions (Aristotle has all the virtues of a philosopher) • Meta-assertions (“You are a good girl” is much to be wished) • Non-declaratives: Questions, commands, absurdities, emotions, music,…

29. Gamma part You can lead a horse to water, but you can’t make him drink

30. Existential Graphs • Explicit, non-inductive definitions • Holistic, non-compositional system of meaning • Semantics in terms of the “Endoporeutic Method” (1905) • Similar to Game-Theoretic Semantics • Utterer vs. Interpreter play the “game” • Perfect information, winning strategies as “habits” of action A.-V. Pietarinen (2003): “Peirce’s Game-theoretic Ideas in Logic”, Semiotica 144, 33-47

31. Proofs in EGs • Four rules of transformation: double negation, insertion, erasure, iteration/deiteration • Sound and complete for Alpha & Beta • Natural deduction system, 30 years before Gentzen and others

32. … … … … Proofs in EGs • Double cut insertion/deletion • Graph insertion: any graph may be added to an odd-polarity area … …

33. Graph erasure: any graph may be erased from an even-polarity area … … … … Proofs in EGs • Iteration/deiteration: any copy of a subgraph may be added/erased to/from the same or deeper areas than it iteration … … … … deiteration

34. Heterogeneous reasoning systems • A hundred years later… • Barwise & Etchemendy’s Hyperproof • John Sowa’s Conceptual Graphs • Semantic networks • Hans Kamp’s Discourse-Representation Theory • Spider diagrams (extending Euler-Venn) …and much more A.-V. Pietarinen (2004): ”Diagrammatic Logic and Game Playing”, Multidisciplinary Studies on Visual Representations and Interpretations, Elsevier.

35. Hyperproof • Given information: a blocks world (toy model, situation) + FOL sentences • Determine what characteristics hold of it

36. Conceptual Graphs A cat is on a mat Every cat is on a mat Tom believes that Mary wants to marry a sailor John Sowa (2000): Knowledge Representation: Logical, Philosophical and Computational Foundations, Brooks/Cole

37. Conceptual Graphs • An open-ended enterprise: • Formal concept analysis • Natural-language processing • Software specification • Information extraction • CGWorld • Prolog+CG (integrates Prolog, CGs, OOP and JAVA)

38. Semantic networks • Concepts, relationships • Boxes, arrows, labels • Database queries, inferences • Non-monotonicity • ER graphs, Dataflows, Petri nets, Neural nets,… • A very heterogeneous field!

39. Discourse-Representation Theory • Hans Kamp (1981), Lauri Karttunen (1976) A man walks in the park. He whistles. T. Janasik, A.-V. Pietarinen and G. Sandu (2003): ”Anaphora and Extensive Games”, Papers from the 38th Meeting of the Chicago Linguistic Society, Chicago Linguistic Society.

40. IF EGs • Can we increase the expressive power of the Beta part of EGs without introducing any new signs? • Yes → make EGs ”Independence-friendly” A.-V. Pietarinen (2004): ”Peirce’s Diagrammatic Logic in IF Perspective”, LNAI 2980, 97-111

41. IF EGs • IF extension of EGs expressive enough so as to capture much of our mathematics • IF EGs model good deal of natural-language utterances, including discourse and branching quantifiers • It illustrates the different logical priorities between LIs, forbidden in graphs on 2D SAs A.-V. Pietarinen (2004): “Compositionality, Relevance, and Peirce’s Logic of Existential Graphs”

42. IF EGs • Non-compositional system: local vs. global contexts • Topological distinction between open/closed sets: area of the cut / area + the cut • Distinction between strong, game-theoretic negation (“~”) as a role switch and classical, contradictory negation (“ ”) as complementation • The latter requires a meta-level definition, whereas the former is processual A.-V. Pietarinen (2004): “Peirce’s Magic Lantern II: Topology, Graphs and Games”

43. Conclusions Peirce envisaged some 3D extension: • “Three dimensions are necessary and sufficient for the expression of all assertions; so that, if man’s reason was originally limited to the line of speech (which I do not affirm), it has now outgrown the limitation” (MS 654: 6, 1910) Peirce Manuscripts at Harvard University & Helsinki, microfilmed 1967, catalogued by R. Robin.

44. Conclusions IF EGs fulfill Peirce’s dream: • “At great pains, I learned to think in diagrams, which is a much superior method [to algebraic symbols]. I am convinced that there is a far better one, capable of wonders; but the great cost of the appatatus forbids my learning it. It consists in thinking in stereoscopic moving pictures.” (MS L 231, 1911)

45. Conclusions • Insufficiency of FOL/Beta Graphs • Symbolic vs. disgrammatic representations • Reasoning with non-linguistic forms • Multi-modal reasoning (perception, tactile etc. stimuli, “tinctured” EGs) • “Free rides” • Corollarial vs. theorematic reasoning

46. The way ahead… • A semantic web using diagrammatic representational systems? • Pragmatics through games • Abstract vs. strategic meaning • Speaker’s vs. literal meaning (interpretants) • The Web: iconic, symbolic, indexical signs • Putting questions to the Web: interrogative games A.-V. Pietarinen (2003): ”The Semantic + Pragmatic Web = the Semiotic Web”, Proc. International IADIS/WWW Conference, IADIS Press, 981-984 A.-V. Pietarinen (2004): ”Peircean and Historical Pragmatics”, Journal of Historical Pragmatics

47. Projects • 2002-2003: the Academy of Finland Project Game-theoretical Semantics and its Applications, Director: Jaakko Hintikka • 2003-2005: the Academy of Finland Project Logic and Game Theory, A.-V. Pietarinen (Post-Doc Fellow) • 2003-2004: the Academy of Finland Project Communications in the 21st Century: The Relevance of C.S. Peirce

48. Commens is a Finnish Peirce studies website, which promotes and supports investigation of Peircean philosophy and sign theory. The Commens pages include introductions to Peirce and his philosophy, original papers, various bibliographies, and other study aids. “...that mind into which the minds of utterer and interpreter have to be fused in order that any communication should take place ... may be called the commens. It consists of all that is, and must be, well understood between utterer and interpreter, at the outset, in order that the sign in question should fulfill its function." (Charles S. Peirce, 1906.) Mats Bergman Erkki Kilpinen Sami Paavola Ahti-Veikko Pietarinen Sami Pihlström … http://www.helsinki.fi/science/commens/