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Syntax and Translation

Syntax and Translation. Gregory 2.3-2.4. The Language S. Vocabulary: Grammatical Categories Statement Letters A, B, C, . . . A 1 , B 1 , C 1 , . . . , Z­ 1­­ , A 2 , . . . Truth-Functional Connectives ¬ , ∧ , ∨ , → , ↔ Punctuation Marks (, ), [, ], {, } Translating English sentences

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Syntax and Translation

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  1. Syntax and Translation Gregory 2.3-2.4

  2. The Language S • Vocabulary: Grammatical Categories • Statement Letters A, B, C, . . . A1, B1, C1, . . . , Z­1­­, A2, . . . • Truth-Functional Connectives ¬ , ∧ , ∨ , → , ↔ • Punctuation Marks (, ), [, ], {, } • Translating English sentences • Statement letters translate simple sentences, which have no proper parts that are themselves sentences • Connectives (‘sentence-forming operators’) build more complex sentences from simpler sentences

  3. 2.3 The Syntax of S Rules for forming WFFs and Syntax Trees

  4. 2.3 Expressions of S An expression of S is any finite sequence of the symbols of S (not necessarily grammatical!) What’s wrong with the expressions on the right?

  5. WFFs (Well-Formed Formulas) of S (1) If ℙ is a statement letter, then ℙ is a wff of S (2) If ℙ and ℚ are wffs of S, then (a) ¬ ℙ is a wff of S (b) (ℙ ∧ ℚ) is a wff of S (c) (ℙ ∨ ℚ) is a wff of S (d) (ℙ → ℚ) is a wff of S (e) (ℙ ↔ ℚ) is a wff of S (3) Nothing is a wff of S unless it can be shown so by a finite number of applications of clauses (1) and (2)

  6. Recursive (‘Inductive’) Definition Basis Clause specifies initial members of the set of things to which the term in question applies • Sentence letters are WFFs of S Recursive (Inductive) Clause specifies how to generate further members of the set of things to which the term applies • Rules for forming sentences using the connectives (parentheses are typographically parentheses, brackets or braces and outer my be dropped). Extremal Clause states that the term applies to only those things specified by the basis and recursive clauses (‘That’s all, folks!’) • Nothing is a WFF of Sunless it’s a result of finite number of applications of above clauses

  7. Atomic & Molecular Formulas, Main Connectives • Any wff that qualifies simply in virtue of clause (1) of the definition of a wff (that is, any wff that just is some statement letter), is called an atomic formula, wff, or sentence. By analogy, all other wffs are molecular. • The main connective of a molecular wff R is the connective appearing in the clause of the definition of a wff cited last in showing R to be a wff. The immediate well-formed components of a molecular wff are the values of P and Q (in the case of clause (2a) simply P) in the last-cited clause of the definition of a wff. The well-formed components of a wff are the wff itself, its immediate well-formed components, and the well-formed components of its immediate well-formed components. The atomic components of a wff are the well-formed components that are atomic wffs. • The scope of a connective is that portion of the wff containing its immediate well- formed component(s).

  8. Syntactic Concepts and Conventions • Atomic wffs have no main connective. • The main connective of a molecular wffℝis the connective appearing in the clause of the definition of a wff cited last in showing ℝto be a wff. The immediate well-formed components of a molecular wff are the values of ℙand ℚ(in the case of clause (2a) simply ℙ) in the last-cited clause of the definition of a wff. • The well-formed components of a wff are the wff itself, its immediate well-formed components, and the well-formed components of its immediate well-formed components. The atomic components of a wff are the well-formed components that are atomic wffs. • Scope: The scope of a connective is that portion of the wff containing its immediate well-formed component(s).

  9. Building WFFs ‘{[(¬ A ∧ B) → C] ∨ (D ↔ E)}’ is a WFF: how did this happen? • ‘A’, ‘B’, ‘C’, ‘D’, and ‘E’ are WFFs by Clause 1 • ‘¬ A’ is a WFF by Clause 2 • ‘(¬ A ∧ B)’ is a WFF by Clause 2 • ‘[(¬ A ∧ B) → C]’ is a WFF by Clause 2 • ‘(D ↔ E)’ is a WFF by Clause 2 • ‘{[(¬ A ∧ B) → C] ∨ (D ↔ E)}’ by Clause 2

  10. 2.3 WFFs and Syntax Trees: p 49 Examples WFFs of S Not WFFs of S (15)  (A73 ) (16) A73 ¬ (18)  ¬ ¬ (𝔻 → E) (13)  (A → B → C) (14)  ((A ∨ ∧ B) ∧ (¬ B → C)) (9)  A73 (10)  ¬A73 (12)  ¬ ¬ (D → E) (13)  ((A → B) → C) (14)  ((A ∨ B) ∧ (¬ B → C))

  11. Syntax tree showing how WFF was built

  12. Scope • Atomic wffs have no main connective. The main connective of a molecular wff R is the connective appearing in the clause of the definition of a wff cited last in showing R to be a wff. • The immediate well-formed components of a molecular wff are the values of P and Q (in the case of clause (2a) simply P) in the last-cited clause of the definition of a wff. The well-formed components of a wff are the wff itself, its immediate well-formed components, and the well-formed components of its immediate well-formed components, etc. The atomic components of a wff are the well-formed components that are atomic wffs. • The scope of a connective is that portion of the wff containing its immediate well- formed component(s).

  13. Identifying WFFs and Main Connectives Write the main connective of each sentence in the space provided if it is a WFF; if it’s not a WFF write ‘X’ ___ A → B ___ (A → B) ∨ C ___ A → (B ∨ C) ___ A → B ∨ C ___ ¬ [A → (B ∨ C)] ___ [(A → B) ∨ C] ∧ (D ↔ E) ___ (A → B) ∨ C ∧ (D ↔ E) ___ (A → B) ∨ [C (D↔ E)] ___ ¬ ¬ ¬ ¬¬ A ___ ¬ (¬ A) → ∧ X ∨ → X ¬ X X ¬ ∨ →

  14. 2.3.2 Syntactic Concepts and Conventions • Outer parentheses (which aren’t doing any work) may be dropped, e.g. • ‘(A ∧ (B ∨ D)) is OK -- and ‘A ∧ (B ∨ C)’ is also OK but… • ‘A ∧B ∨ C is NOT OK (note ambiguity) • Atomic Formula, Molecular Formula • Any wff that qualifies simply in virtue of clause (1) of the definition of a wff (that is, any wff that just is some statement letter), is called an atomic formula, wff, or sentence. By analogy, all other wffs are molecular.

  15. 2.4 Symbolization Translating English Sentences into the Language of S

  16. Negation, Conjunction, Disjunction • S doesn’t allow compound subjects or predicates E.g. Dick and Jane both went = Dick went and Jane went = D ∧ J • DeMorgan’s Laws: neither…nor... ; not both...and... ¬ (ℙ ∨ ℚ) ⇔ (¬ ℙ ∧ ¬ ℚ) Neither ℙ nor ℚ ⇔ Not ℙ and not ℚ ¬ (ℙ ∧ ℚ) ⇔ (¬ ℙ ∨ ¬ ℚ) Not both ℙ and ℚ ⇔ Not ℙor not ℚ Examples: She was neither young nor beautiful. ¬ (Y ∨ B) or ¬ Y ∧ ¬ B You can’t both have your cake and eat it. ¬ (H ∧ E) or ¬ H ∨ ¬ E

  17. De Morgan’s Laws in Logic and Set Theory • the negation of a disjunction is the conjunction of the negations; and the negation of a conjunction is the disjunction of the negations. ¬ (ℙ ∨ ℚ) ⇔ (¬ ℙ ∧ ¬ ℚ) Neither ℙ nor ℚ ⇔ Not ℙ and not ℚ ¬ (ℙ ∧ ℚ) ⇔ (¬ ℙ ∨ ¬ ℚ) Not both ℙ and ℚ ⇔ Not ℙ and not ℚ • the complement of the union of two sets is the same as the intersection of their complements; and the complement of the intersection of two sets is the same as the union of their complements. (A ⋃ B)c =(Ac ⋂ Bc) Complement A union B = complement A intersection complement B (A ⋂ B)c =(Ac ⋃ Bc) Complement A intersection B = complement A union complement B

  18. Things that are neither A nor B Venn Diagrams represent sets Things that are both A and B Things that are B but not A Things that are A but not B A B U

  19. Union, Intersection, Complement • Fig 1 represents A union B in yellow • Blue is complement of A union B--and intersection of complements of A and B • Fig 2 represents A intersection B in yellow • Blue is complement of A intersection B--and union of complements of A and B

  20. You can’t both have have cake and eat it. Venn Diagrams represent sets Nothing here! Havers Eaters U

  21. She was neither young nor beautiful. Venn Diagrams represent sets She isn’t anywhere here! Young Beautiful U

  22. Translation: not both…and, neither...nor • You can’t both have your cake and eat it. ¬ (H ∧ E) or ¬ H ∨ ¬ E or H → ¬ E or E → ¬ H … • She was neither young nor beautiful. ¬ (Y ∨ B) or ¬ Y ∧ ¬ B • Sweet or cheese but not both. (S ∨ C) ∧ ¬ (S ∧ C) • Working hard is neither necessary nor sufficient for success ¬ [(S → W) ∨ (W → S)]

  23. 2.4.2 Translation Exercises 1 The Falcons do not score a goal ¬ G 2 The Falcons and the Mustangs win their semifinal matches. W ∧ V 3 Either the Falcons or the Mustangs win the Cup. F ∨ M 4 Santacruz plays for the Falcons but Khumalo does not. S ∧ ¬ K 5 Khumalo either does or does not play for the Falcons. K ∨ ¬ K

  24. 2.4.2 Exercises 6 Neither the Falcons nor the Mustangs win the cup ¬ (F ∨ M) 7 Both the Falcons and the Mustangs don’t win the cup ¬ F ∧ ¬ M 8 Not both the Falcons and the Mustangs win the Cup ¬ (F ∧ M) 9 Either the Falcons or the Mustangs do not win the Cup ¬ F ∨ ¬ M 10 Santacruz plays for the Falcons and captains the Falcons, but does not play for the Mustangs. (S ∧ C) ∧ ¬ O

  25. 2.4.2 Exercises 11 Either Nakata and Khumalo both play for the Falcons, or Khumalo plays for the Mustangs. (N ∧ K) ∨ O 12 Nakata plays for the Falcons, and Khumalo plays for either the Falcons or the Mustangs N ∧ (K ∨ O) 13 Either Khumalo, Nakata, or Santacruz plays for the Falcons K ∨ (N ∨ S) or (K ∨ N) ∨ S 14 Either both teams score a goal, or neither team wins the Cup. (G ∧ H) ∨ ¬ (F ∨ M) 15 Santacruz plays for and captains the Falcons, and either they score a goal or they don’t win the Cup (S ∧ C) ∧ (G ∨ ¬ F)

  26. Conditionals and Biconditionals • Antecedent sufficient for consequent; consequent necessary for antecedent. Example: If x is a dog then x is a mammal • Being a dog is a sufficient condition for being a mammal. • Being a mammal is a necessary condition for being a dog. • Necessary and Sufficient Conditions ℙ → ℚ If P then Q, P only if Q, Q, if P P is sufficient for Q, Q is necessary for P ℙ ↔ ℚ P if and only if Q P is necessary and sufficient for Q (and vice versa)

  27. Translating Conditionals and Biconditionals

  28. Necessary & Sufficient Conditions • ‘Necessary’ and ‘sufficient’ mean exactly what you think they mean! • ‘Necessary’ means ‘required’ • Being at least 21 is a necessaryconditionfor drinking legally in California. • ‘Sufficient’ means ‘enough’ • A blood alcohol level of exactly 0.08 isa sufficient condition onbeing legally drunk in California.

  29. Necessary and Sufficient Conditions

  30. is sufficient for Necessary & Sufficient Conditions • The state of affairs described in the antecedent is asserted to be a sufficient condition on the state of affairs described in the consequent. • The state of affairs described in the consequent is asserted to be a necessarycondition on the state of affairs described in the antecedent. If it rains then it pours. is necessary for

  31. Antecedent Sufficient/Consequent Necessary • If someone is a mother then they’re female • If you know that someone is a mother, that’s enough to tell you that person is female, so being a mother is a sufficient condition on being female. • Being a mother is not a necessarycondition on being female since you can be female without being a mother. • Being female is necessary for being a mother: if someone is not female they can't possibly be a mother. • Thus (1) says that being a mother is a sufficientcondition on being female and being female isa condition on being a mother.

  32. Necessary, Sufficient, Both, or Neither? sufficient • Being a dog is __________ for being a mammal. • Being a mammal is __________ for being a dog. • Paying your tuition is __________ graduation from USD. • Getting a 95% is __________ for getting an ‘A’ in this course. • Coming to every class meeting is __________ for passing this course. • x being odd is __________ for xy being odd. • x being even is __________ for xybeing even. • x and y being both being odd is __________ for xybeing odd. necessary necessary sufficient neither necessary sufficient necessary sufficient

  33. Contrapositive • The contrapositive of a conditional is the result of flipping and negating its antecedent and consequent. • The contrapositive of ‘If P then Q’ is ‘If NOT-Q then NOT-P. • A conditional is logically equivalent to its contrapositive • P and Q are logical equivalent iff they necessarily have the same truth value. • This explains why we understand the consequent of a conditional as a necessary condition for the antecedent. • If Amalasuntha is a dog then Amalasuntha is a mammal. • If Amalasuntha is not a mammal then Amalasuntha is not a dog.

  34. Amalasuntha

  35. 2.4.4 Exercises 1 If Nakata plays for the Falcons, then the Falcons win the Cup. N → F 2 The Falcons score a goal, if Khumalo plays for them. K → G 3 The Falcons score a goal only if Khumalo plays for them. G → K 4 The Falcons score a goal if and only if Khumalo plays for them. G ↔ K 5 Santacruz plays for the Falcons, assuming she doesn’t play for the Mustangs. ¬ Z → S

  36. 2.4.4 Exercises 6 The Falcons winning their semifinal match is necessary for their winning the Cup. F → W 7 The Falcons winning the final match is sufficient for their winning the Cup. L → F 8 The Falcons winning the final is necessary and sufficient for winning the Cup. T ↔ F 9 The Mustangs win the Cup unless the Falcons score a goal. ¬ G → M 10 Unless Santacruz doesn’t play for the Falcons, the Mustangs will not win the Cup. ¬ ¬ S → ¬ M or S → ¬ M or M → ¬ S or ¬ S ∨ ¬ M

  37. Complex Symbolization • Assuming Nakata and Khumalo play for the Falcons, the Falcons will win the Cup. (N ∧ K) → F  • The Falcons win the Cup only if Santacruz plays for and captains the Falcons. F → (S ∧ C) • Santacruz must play for and captain the Falcons, if they are to win the Cup. F → (S ∧ C) • The Falcons win the Cup if and only if they win both their semifinal and final matches. F ↔ (W ∧ L) • If Santacruz and Khumalo don’t both play for the Mustangs, then the Mustangs will win the Cup only if Santacruz or Nakata doesn’t play for the Falcons. ¬ (Z ∧ Ο) → [M → (¬ S ∨ ¬ N)] or (¬ Z ∨ ¬ O) → [M → ¬ (S ∧ N)]

  38. Complex Symbolization: Punctuation • If Santacruz and Khumalo don’t both play for the Mustangs, then the Mustangs will win the Cup only if Santacruz or Nakata doesn’t play for the Falcons. ¬ (Z ∧Ο) → [M → (¬ S ∨ ¬ N)] or (¬ Z ∨ ¬ O) → [M → ¬ (S ∧ N)] • If the Falcons and the Mustangs win their semifinal matches, then either the Falcons or the Mustangs win the Cup, but not both (W ∧ V) → [(F ∨ M) ∧ ¬ (F ∧ M) or (W ∧ V) → (¬ F ↔ M) • Either the Falcons win the Cup or Nakata doesn’t play for them; moreover Nakata doesn’t play for them. (F ∨ ¬ N) ∧ ¬ N • If Santacruz plays for the Falcons, then if she captains the Falcons then the Falcons will score a goal and win the cup. F → [C → (G ∧ F)]

  39. Parentheses, Braces, & Brackets: Punctuation • I’ll go to Amsterdam and Brussels or Calais • This is ambiguous and we can’t tolerate ambiguity! Brussels AND Amsterdam OR Calais Amsterdam Brussels OR AND Calais

  40. Parentheses, Brackets & Braces: Punctuation • Grouping devices avoid ambiguity (for “unique readability”): • I’ll go to Amsterdam, and then to either Brussels or Calais: A ∧ (B ∨ C) • I’ll either go to Amsterdam and Brussels, or else to Calais: (A ∧ B) ∨ C Brussels AND Amsterdam OR Calais Amsterdam Brussels OR AND Calais

  41. 2.4.6 Exercises 1. Santacruz plays for the Falcons or the Mustangs, but she does not captain the Falcons. (S ∨ Z) ∧ ¬ C 2. Either Nakata and Khumalo play for the Falcons, or Santacruz plays for the Mustangs . (N ∧ K) ∨ Z 3. Either the Falcons or the Mustangs win the Cup, but not both. (F ∨ M) ∧ ¬ (F ∧ M) 4. The Falcons and the Mustangs both win their semifinal match, and the Mustangs or the Falcons don’t win the Cup. (W ∧ V) ∧ (¬ M ∨ ¬ F)

  42. 2.4.6 Exercises 5. Either Santacruz plays for the Falcons and the Falcons score a goal, or Khumalo plays for the Mustangs and the Mustangs score a goal. (S ∧ G) ∨ (O ∧ ¬ F) 6. The Falcons win the Cup if and only if either Nakata or Santacruz play for them. F ↔ (N ∨ S) 7. If the Mustangs won their semifinal match but did not win the Cup, then they did not win the final match. (V ∧ ¬ M) → ¬ T 8. The Falcons will not win the Cup unless Nakata plays for them. ¬ N ∨ ¬ F or F → N or N ∨ ¬ F …

  43. 2.4.6 Exercises 9. Unless Santacruz and Khumalo both play for the Falcons, the Mustangs will win the Cup. (S ∧ K) ∨ M or ¬ M → (S ∧ K) or ¬ (S ∧ K) → M 10. Only if Nakata plays for the Falcons and the Mustangs don’t score a goal, will the Falcons win the final match and the Cup. (L ∧ F) → (N ∧ ¬ H) 12. For the Falcons to score a goal it is necessary that Santacruz and Khumalo play for them. G → (S ∧ K) 13. For the Falcons to win the final match and the Cup it is sufficient that Santacruz plays for them and captains them. (S ∧ C) → (L ∧ F)

  44. 2.4.6 Exercises 13. If Khumalo, Nakata, and Santacruz all play for the Falcons, then the Mustangs will not score a goal nor will they win the Cup. [(K ∧ N) ∧ S] → (¬ H ∧ ¬ M) or [(K ∧ N) ∧ S] → ¬ (H ∨ M) 14. The Falcons score a goal and win the Cup if Santacruz and Khumalo play for them, and only if Santacruz and Khumalo play for them. (S ∧ K) → (G ∧ F) 15. If Khumalo and Santacruz play for the Mustangs, then if Nakata doesn’t play for the Falcons, then the Falcons will win the Cup only if the Mustangs don’t score a goal. (O ∧ Z) → [¬ N → (F → ¬ H)]

  45. 2.5 Alternate Symbols and Other Choices Cultural enrichment only: you will not be tested ;-)

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