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- Newsgroups: sci.math
- Path: sparky!uunet!spool.mu.edu!news.nd.edu!mentor.cc.purdue.edu!hrubin
- From: hrubin@mentor.cc.purdue.edu (Herman Rubin)
- Subject: definitions vs. characterizations (inspired by "What's a manifold?")
- Message-ID: <BxCnq6.8wr@mentor.cc.purdue.edu>
- Organization: Purdue University Statistics Department
- References: <COLUMBUS.92Nov6105242@strident.think.com> <1df8leINNolm@iskut.ucs.ubc.ca>
- Distribution: sci
- Date: Sat, 7 Nov 1992 14:18:05 GMT
- Lines: 32
-
- In article <1df8leINNolm@iskut.ucs.ubc.ca> ramsay@unixg.ubc.ca (Keith Ramsay) writes:
- >In article <COLUMBUS.92Nov6105242@strident.think.com>
- >columbus@strident.think.com (Michael Weiss) writes:
- >|I would summarize almost all the discussion in favor of the atlas
- >|definition of a manifold in one phrase:
-
- >| proofs drive definitions
-
- >|in other words, old, "intuitive" definitions are replaced by new "abstract"
- >|definitions when the new definitions turn out to be more convenient for the
- >|logical development of the subject.
-
- >This is also one of the main points of _Proofs_and_Refutations_ by
- >Imre Lakatos. His example is the concept of "polyhedron".
-
- The problem is that we are using definitions instead of characterizations.
- There are dozens of definitions of "group" and of "topological space."
- The concepts of group and topological space do not depend on which subset
- of their properties we choose to use to characterize them.
-
- In other situations, the definitions are at best stultifying. The general
- notion of indepandence in probability is that of obtaining no probability
- information about some of the objects from information about others. This
- is not how one tests for independence, as it is extremely complicated to
- use directly. The usual "definition", namely, probabilities of intersections
- equal products of probabilities, is a much simpler test. But as a definition,
- it conveys little.
- --
- Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
- Phone: (317)494-6054
- hrubin@snap.stat.purdue.edu (Internet, bitnet)
- {purdue,pur-ee}!snap.stat!hrubin(UUCP)
-