Zermelo–Fraenkel set theory - Quiz
  • 1. Which set theory axioms form ZF?
A) Axioms 1–9
B) Axioms 1–8
C) Axioms 1–7
D) Axioms 2–9
  • 2. What is the equivalent of the axiom of choice used by Kunen (1980) to turn ZF into ZFC?
A) The axiom of regularity
B) The axiom of infinity
C) The axiom of extensionality
D) The well-ordering theorem
  • 3. Why is it unnecessary to have a separate axiom asserting that at least one set exists?
A) It is assumed that the domain of discourse is empty
B) It is a theorem of first-order logic that something exists
C) The axiom of specification implies it
D) The axiom of extensionality implies it
  • 4. Under what condition does the axiom of infinity ensure that a set exists?
A) In free logic where first-order logic does not prove existence
B) It only exists in the axiom of pairing
C) It is only guaranteed if the domain is finite
D) It is never guaranteed by the axiom of infinity
  • 5. What does the axiom of extensionality state?
A) No set is an element of itself
B) Every set has a unique subset
C) Two sets are equal if they have the same rank
D) Two sets are equal if they have the same elements
  • 6. What is another name for the axiom of regularity?
A) The axiom of union
B) The axiom of foundation
C) The axiom of substitution
D) The axiom of specification
  • 7. What does the axiom of regularity imply about a non-empty set?
A) It is an element of itself
B) It contains an empty set
C) It must be infinite
D) It contains a member disjoint from itself
  • 8. With the axioms of pairing and union, what does the axiom of regularity imply?
A) Every set is unique
B) There exists an empty set
C) All sets are finite
D) No set is an element of itself
  • 9. What are other names for the axiom schema of specification?
A) Axiom of choice or foundation
B) Axiom of infinity or union
C) Axiom of separation or restricted comprehension
D) Axiom of identity or equality
  • 10. Why is the axiom schema of specification restricted to constructing subsets?
A) To increase the speed of proofs
B) To avoid Russell's paradox
C) Because sets cannot contain other sets
D) To force the existence of the empty set
  • 11. What is the result of applying unrestricted comprehension in naive set theory?
A) The well-ordering theorem
B) The existence of an ordinal rank
C) Russell's paradox
D) The uniqueness of the empty set
  • 12. How can the existence of the empty set be proven using the axiom schema of specification?
A) By using a property that no set has
B) By the axiom of extensionality
C) By the axiom of regularity
D) By the axiom of infinity
  • 13. What does the axiom of extensionality imply about the empty set?
A) It is unique
B) It contains itself
C) It depends on the set w
D) It does not exist
  • 14. According to the text, what does the axiom of infinity, replacement, and union imply together?
A) Russell's paradox is resolved
B) Every set has an ordinal rank
C) The empty set does not exist
D) The axiom of choice is unnecessary
  • 15. Who are the mathematicians that Zermelo–Fraenkel set theory is named after?
A) Ernst Zermelo and Abraham Fraenkel
B) Bertrand Russell and Paul Bernays
C) Kurt Gödel and John von Neumann
D) Georg Cantor and Gottlob Frege
  • 16. What is another name for the collection of all sets used to interpret the axioms?
A) The Russellian hierarchy
B) The Zermelo collection
C) The von Neumann universe
D) The Fraenkel universe
  • 17. What is the name of the cardinal number that Zermelo's theory could not prove existed?
A) aleph-zero
B) aleph-null
C) aleph-one
D) aleph-omega
  • 18. How is the equality sign usually treated in ZFC?
A) As a set operator
B) As a quantifier
C) As a non-logical predicate
D) As a primitive logical symbol
  • 19. The symbol ∈ represents what kind of relation?
A) A binary relation
B) A ternary relation
C) A unary relation
D) An equality relation
  • 20. How many variables are in the alphabet of the formal language?
A) An uncountable number
B) A finite number
C) A countably infinite number
D) Zero
  • 21. Which of the following is an atomic formula construction?
A) ∀xϕ
B) x ∧ y
C) x = y
D) ¬x
  • 22. How many well-formed formulae exist in the formal language L?
A) Finitely many
B) Uncountably infinitely many
C) Only one
D) Countably infinitely many
  • 23. Which symbol represents the interpretation of the membership relation in the structure S?
A) mu
B) I_in
C) phi
D) psi
  • 24. What is the function mu in the structure S?
A) Membership relation
B) Truth value function
C) Variable assignment function
D) Domain interpretation function
  • 25. What does the expression S |= phi represent?
A) S is a subset of phi
B) S contains phi
C) S is equivalent to phi
D) S satisfies phi
  • 26. What are phi and psi metavariables for?
A) Any constant
B) Any wff
C) Any domain element
D) Any variable
  • 27. The variable assignment function mu maps variables to elements of which set?
A) A
B) D
C) The set of relations
D) The set of wffs
  • 28. In the context of S |= phi, what does phi mean?
A) phi is the interpretation of S
B) S assigns phi to the domain
C) S makes phi true
D) phi is a member of D
  • 29. In the axiom schema of replacement, if φ represents a definable function f, what represents its domain?
A) A
B) w1
C) B
D) φ
  • 30. Which variable is restricted from being free in the formula φ for the axiom schema of replacement?
A) B
B) x
C) y
D) A
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