> In some sense that's defendable (that what could call natural numbers is > a cultural question or historical, like looking at what Peano did nor > did not define). > On the other hand, one normally does not just deals with the numbers as > such, one does something with it (like comparing them or calculating > with them). If one takes the reservoir of numbers (in decimal notation, > {0,1,2,3 .....} indeed it is irrelelvant where to start, 0,1, or > 23. Also if one does nothing else than comparing them (that would be > considering them as "ordinals", one has one single smallest number, and > again it's it's irrelevant if that's ``called'' nor notated $0$, "zero" > or "1", or "23". > Now, if one starts doing simple calculations (addition, multiplication), > the natural numbers including 0 is simply more "elegant" or ``richer'' > than without. One has laws like n+0 = n, n*0=0 (one then says, 0 is a > neutral element wrt. +, there is terminology for all than, and it's > simply that N with 0 has nicer ``algebraic'' characteristics than > without. It's quite analogous to the choice between defining lists as to > include the empty list '() as a ``natural'' list, or insist on that > ``natural'' lists must have 1 or more elements. > Foundational folks can elaborate on that analogy between lists and nats, > but as you say, in both cases they favor to include 0 to nats and the > empty list to lists (and there are more examples) and it's favored for > good reasons (at least to them). That is the first time I remember that on this list, questions of the foundation of mathematics are discussed 😉 Back to the point, maybe I am too conservative, but I would include 0 within the natural numbers, and the example I started with, needs to cover that case (student marks range between 0 to 10 both included), so sorting should work (for me) in that case. I don't see, so far any benefit for not considering 0 in that sorting process. -- I strongly condemn Putin's war of aggression against the Ukraine. I support to deliver weapons to Ukraine's military. I support the ban of Russia from SWIFT. I support the EU membership of the Ukraine.
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