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  "body": "\n## Summary\n\nSet theory is the branch of mathematical logic that studies [[sets|0BSJ7RQ9BW]], collections of objects called their [[elements|0EZ758XE73]].\nCantor created it in the 1870s, with his study of infinite sets and their sizes.\nIn its axiomatic form, most often [[Zermelo–Fraenkel set theory|0HE5WDQ9FJ]] with choice, it serves as the standard foundation of mathematics.\nIts own subjects include ordinals and cardinals, independence results, large cardinals and descriptive set theory.\n\n## Explanations\n\n### L1 human\n\nAlmost every mathematical object can be built from sets.\nFor example, the number $2$ can be taken to be the set $\\set{\\emptyset, \\set{\\emptyset}}$, and a function is a set of ordered pairs.\nSet theory writes down the basic rules for sets, and then studies what follows from them.\nA famous discovery is that infinite sets come in different sizes: there are more real numbers than natural numbers.\nAnother is that some natural questions, such as the continuum hypothesis, cannot be settled by the usual rules.\n",
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