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<blockquote style="position: relative; padding-left: 55px;"><section><a href="https://mas.to/users/JorgeStolfi/statuses/113498369012472397">Jorge Stolfi (jorgestolfi@mas.to)'s status on Sunday, 17-Nov-2024 21:47:54 JST</a><a href="https://mas.to/@JorgeStolfi" title="jorgestolfi@mas.to"><img src="https://gnusocial.jp/avatar/88727-48-20240330171544.webp" width="48" height="48" alt="Jorge Stolfi" style="position: absolute; left: 0; top: 0;">Jorge Stolfi</a><div><a href="https://gnusocial.jp/notice/7848300" rel="in-reply-to">in reply to</a><ul><li><li><a href="https://gnusocial.jp/user/92115" title="dymaxion@infosec.exchange">Eleanor Saitta</a></li><li><a href="https://gnusocial.jp/user/92455" title="whknott@mastodon.social">Wyatt H Knott</a></li></ul></div></section><article><p><a href="https://sauropods.win/@futurebird">@futurebird</a> <a href="https://infosec.exchange/@dymaxion">@dymaxion</a> <a href="https://mastodon.social/@whknott">@whknott</a> </p><p>"Let X be the set of all elements that don't belong to X"  That definition of the set X is *obviously* invalid; but how do you define rigorously what is a valid definition?</p><p>The complement C of a set X is supposed to be all the elements that do not belong to X.  But since  sets can be elements of other sets, the set C is itself an element of C. Is that okay? if not, how do we fix that?🧵&gt;</p></article><footer><a rel="bookmark" href="https://gnusocial.jp/conversation/4012638#notice-7848301">In conversation</a><time datetime="2024-11-17T21:47:54+09:00" title="Sunday, 17-Nov-2024 21:47:54 JST">about a year ago</time> <span>from <span><a href="https://mas.to/@JorgeStolfi/113498369012472397" rel="external" title="Sent from mas.to via ActivityPub">mas.to</a></span></span><a href="https://mas.to/@JorgeStolfi/113498369012472397">permalink</a></footer></blockquote>

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Jorge Stolfi (jorgestolfi@mas.to)'s status on Sunday, 17-Nov-2024 21:47:54 JSTJorge Stolfi
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@futurebird @dymaxion @whknott
"Let X be the set of all elements that don't belong to X" That definition of the set X is *obviously* invalid; but how do you define rigorously what is a valid definition?
The complement C of a set X is supposed to be all the elements that do not belong to X. But since sets can be elements of other sets, the set C is itself an element of C. Is that okay? if not, how do we fix that?🧵>
In conversationabout a year ago from mas.topermalink

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