Path: ...!eternal-september.org!feeder3.eternal-september.org!i2pn.org!i2pn2.org!.POSTED!not-for-mail From: joes Newsgroups: sci.math Subject: Re: The reality of sets, on a scale of 1 to 10 [Was: The non-existence of "dark numbers"] Date: Tue, 25 Mar 2025 08:27:29 -0000 (UTC) Organization: i2pn2 (i2pn.org) Message-ID: References: <9e0c7e728f7de44e13450d7401fe65d36c5638f3@i2pn2.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Tue, 25 Mar 2025 08:27:29 -0000 (UTC) Injection-Info: i2pn2.org; logging-data="1657017"; mail-complaints-to="usenet@i2pn2.org"; posting-account="nS1KMHaUuWOnF/ukOJzx6Ssd8y16q9UPs1GZ+I3D0CM"; User-Agent: Pan/0.145 (Duplicitous mercenary valetism; d7e168a git.gnome.org/pan2) X-Spam-Checker-Version: SpamAssassin 4.0.0 Bytes: 2661 Lines: 24 Am Mon, 24 Mar 2025 20:17:45 +0100 schrieb WM: > On 23.03.2025 22:28, Alan Mackenzie wrote: >> WM wrote: >>> On 22.03.2025 12:31, joes wrote: >> >>>> for infinite sets "reality" and cardinality don't have to correspond. >>> So it is! Substance and cardinality have nothing in common because >>> sets of very different substance have same cardinality. >> What is this "reality" or "substance" of which you speak? > Substance is by far the better word. It denotes the number of elements. > The set {1, 2, 3} has more substance than the set {7, 14}. For many sets > the relative substance cannot be determined. But this drawback is less > disastrous than to lump every countable set together. You can just say subsets. >> The cardinality of N is aleph-0. >> What is the "reality" (in this sense) of N? > The substance of ℕ is |ℕ|. It is larger than every finite set. The > substance of the set of prime numbers is far less than |ℕ| but larger > than every finite set. These are useful mathematical findings. What's the use? -- Am Sat, 20 Jul 2024 12:35:31 +0000 schrieb WM in sci.math: It is not guaranteed that n+1 exists for every n.