Logic Matters - forall x (Set Theory Chapter)
Unknown
Peter Smith's free study guide to mathematical logic, recommending and comparing textbooks for each core area. Its set theory chapter maps a reading path from naive sets through the ZFC axioms, ordinals and cardinals, helping self-learners choose which texts to tackle first.
More resources on Zermelo-Fraenkel Axioms
Wolfram MathWorld
MathWorld is an online mathematics encyclopedia from Wolfram Research offering detailed, browsable articles on topics across the math spectrum, including algebra, geometry, calculus, and number theory. Each entry includes definitions, theorems, formulas, diagrams, worked examples, and links to further reading.
Stanford Encyclopedia of Philosophy - Set Theory
Joan Bagaria's peer-reviewed Stanford Encyclopedia of Philosophy entry surveying modern set theory: the ZFC axioms, ordinals and cardinals, the continuum hypothesis, forcing and independence results, large cardinals, and determinacy. Readers gain a map of the field's central questions and results.
MATH 320 - Set Theory (METU lecture course)
Thirty-six recorded lectures from a full semester of axiomatic set theory at Middle East Technical University, worked through on the board: the ZFC axioms and their consequences, the number systems built from sets, ordinals, cardinals and the von Neumann hierarchy.
Set Theory (Studies in Logic, Vol. 34)
Graduate treatment of what ZFC can and cannot prove. Formalises the axioms, builds the von Neumann hierarchy, absoluteness and Godel's constructible universe, then develops forcing to establish the independence of the continuum hypothesis and the axiom of choice.
Introduction to Mathematical Thinking
Stanford course by Keith Devlin on how mathematicians reason, starting with the logic of language (and, or, not, implication, quantifiers) and moving to the structure of proofs, including contradiction and induction. Learners become able to read, construct and critique simple mathematical proofs.