Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site pucc-i Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!ihnp4!inuxc!pur-ee!CS-Mordred!Pucc-H:Pucc-I:ags From: ags@pucc-i (Seaman) Newsgroups: net.math Subject: Pedantic questions and circularity Message-ID: <218@pucc-i> Date: Thu, 23-Feb-84 09:35:48 EST Article-I.D.: pucc-i.218 Posted: Thu Feb 23 09:35:48 1984 Date-Received: Fri, 24-Feb-84 02:42:06 EST Organization: Purdue University Computing Center Lines: 26 Now that we know how to prove that all natural numbers can be represented with finitely many digits, would anyone care to prove that every natural number is less than 2**n for some n? I can think of an easy proof that begins by assuming that every number has finitely many digits... Seriously, neither of the above properties of natural numbers comes from the definition. If you want to avoid circularity, you had better start with the Peano Axioms. That is the only way you can know you are talking about the natural numbers, and not about something else. Here is a restatement of the Fifth Peano Axiom which I looked up last night. This version does not mention sets: (5) Let P be a property which is true of zero, and which is true of the successor of any number which has the property. Then P is true of all natural numbers. -- Dave Seaman ..!pur-ee!pucc-i:ags "Against people who give vent to their loquacity by extraneous bombastic circumlocution."