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