Re: Question: Given |X|>0 and |Y|>0, can X x Y be empty?

On Aug 8, 4:54 pm, Scott <ToaTe...@xxxxxxxxx> wrote:

Read a book: I have "Set Theory and its Philosophy" and "The Joy of
Sets".

'Set Theory And It's Philosophy' is a real nice book and with a great
reputation, but I don't know that it's among the best to fill the role
of an introductory text, since its approach, while equivalent (as I
understand) to the standard theory, takes a much different route and
so it might not allow you to communicate as easily with most people
who have not taken the route used in that book..

I've looked at 'The Joy Of Sets' but not studied in it. It too has a
good reputation, but I wonder whether it is among the best to serve as
an introductory text.

Propose, find flaw, learn, repeat.

That might be productive for certain kinds of investigations, but you
need also to KNOW, on your OWN (at least in such rudimentary
situations as in this thread), when you have proposed a correct proof.
You need to know at least one method of, say, natural deduction that
you can refer to so that even for informal proofs you can see to a
certainty (at least as far as anything could be certain) that your
argument is justified (if you were to formalize) at each step by the
rules of some natural deduction calculus (or whatever your preferred
system).

How does one "do" logic? I
always thought it was find a problem or propose a theory and back it
up with proofs.

Get your skills SOLID in some system of predicate calculus first.

MoeBlee

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