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{{DISPLAYTITLE: The middle attic}}
[[File:StAugustineLighthouse.jpg | thumb | St. Augustine Lighthouse photo by Madrigar]]

Welcome to the middle attic, where the uncountable cardinals, that solid stock of mathematics, begin their endless upward structural progession. Here, we survey the infinite cardinals whose existence can be proved in, or is at least equiconsistent with, the ZFC axioms of set theory.

* into the [[upper attic]]
* [[correct]] cardinals, [[reflecting | $V_\delta\prec V$]] and the [[reflecting#Feferman theory | Feferman theory]]
* [[reflecting#Sigma_2 correct cardinals | $\Sigma_2$ correct]] and [[reflecting | $\Sigma_n$-correct]] cardinals
* [[extendible#-extendible cardinals | 0-extendible]] cardinal
* [[extendible#Sigma_n-extendible cardinals|$\Sigma_n$-extendible]] cardinal
* [[beth#beth_fixed_point | $\beth$-fixed point]]
* the [[beth]] numbers and the [[beth | $\beth_\alpha$ hierarchy]]
* [[beth omega | $\beth_\omega$]] and the [[strong limit]] cardinals
* [[Theta | $\Theta$]]
* the [[continuum]]
* [[cardinal characteristics]]  of the continuum
** the [[bounding number | bounding number $\frak{b}$]], the [[dominating number | dominating number $\frak{d}$]], the [[covering number | covering numbers]], [[additivity number | additivity numbers]] and many more
* the [[descriptive set theory | descriptive set-theoretic]] cardinals
* [[aleph#aleph fixed point | $\aleph$-fixed point]]
* the [[aleph]] numbers and the [[aleph | $\aleph_\alpha$ hierarchy]]
* [[Buchholz's ψ functions]]
* [[aleph#aleph omega | $\aleph_\omega$]] and [[singular]] cardinals
* [[aleph#aleph two | $\aleph_2$]], the second uncountable cardinal
* [[uncountable]], [[regular]] and [[successor]] cardinals
* [[aleph#aleph one | $\aleph_1$]], the first [[uncountable]] cardinal
* [[cardinal | cardinals]], [[infinite]] cardinals
* [[Aleph zero | $\aleph_0$]] and the rest of the [[lower attic]]