NO, Cantor's diagonal argument construct a diagonal r that differs
from every element of a COUNTABLE set of reals by a finite initial
segment n(r). You are just not getting Cantor's argument. Cantor's
argument is not about diagonalizing the set of ALL reals since that is
clearly not possible, Cantor's argument is about diagonalizing any
COUNTABLE set of reals. So again for any *countable* set S of reals
there is a diagonal r that differs from each real in S by a finite
initial segment n(r).
This has been PROVED by Cantor. This logically entails that the set R
of ALL reals cannot be countable, since otherwise this leads to the
obvious contradiction that R is missing a member of it which cannot
be.
The complete infinite binary tree have paths that can represent any
real! So no diagonal path can be defined over the whole set, this is
clear. But again also using Cantor's argument we can prove that for
Any subtree T of the complete infinite binary tree if T has countably
many paths then we can define a diagonal path that is missing from T,
i.e. a diagonal path that belongs to the complete infinite binary tree
but yet missing from T. Thus the infinite binary tree itself cannot be
countable!
I reviewed your writings about the infinite binary tree. You want to
prove that if we assume completed infinity (which you don't believe it
to be a consistent assumption, so you don't believe even in the
possible existence of such objects that are completed infinite sets)
then we will arrive at a contradiction, this contradiction is the
Cantor-WM contradiction, that is:
If we assume that the sets N and R of all naturals and reals
respectively are completed infinite sets, then it follows that
(1) R is strictly bigger than N by Cantor's proof
(2) R is as big as N by the WM infinite binary tree proof
Thus R is both as big and not as big as N. A flagrant contradiction!
Thus our assumption that N and R are completed infinite sets is FALSE.
That was the line of your thought.
But unfortunately you couldn't prove (2), your alleged infinite binary
tree proof is simply flawed. I have examined it and reviewed your
writing and replies to posters here and there, all of them do not show
any proof. You have many many errors in your logical steps, one of
them is the one I just showed above. Of course If you manage to prove
that R is as big as N by any argument, then of course you'll be wright
in saying that no completed infinite sets of naturals and reals could
ever exist. But so far, you couldn't.
The main problem with your binary tree proof is that you keep
insisting on the obvious error of identifying the complete infinite
binary tree by its nodes, while a tree is generally identified by the
ordered pair of the set of all its nodes and the set of all its EDGES.
You think that once you've discerned the nodes of your tree then
that's it any tree that have those nodes would be it. Which is wrong,
I can simply construct another tree that completely differ from the
infinite complete binary tree and yet using the nodes of the complete
infinite binary tree themselves. So what identifies the complete
infinite binary tree, and any tree actually, and even any graph is the
set of all nodes and the set of all Edges of it, you keep forgetting
the edges.
Now the reals correspond to PATHS of the complete infinite binary
tree, that's correct! And there is no proof whatsoever up till today
that proves the number of those paths to be countable. We know that
the number of NODES of the complete binary tree is countable, we know
that you can identify every finite path of that tree (that is uni-
directional and that begins with the root node) with the end node of
it, and thus we know that we do have countably many finite paths of
the complete infinite binary tree. But that is not enough! for your
purposes you need to prove that the set of ALL PATHS whether finite or
infinite of the complete infinite binary tree is countable. Which you
haven't done. At last you had to resort to countability of infinite
paths by linking them to finitely many words that can describe them,
which is an argument that has nothing to do with the structure of the
infinite binary tree.And to address it Cantor was not speaking about
the subset of reals that is definable or actually describable by
finite words, he was speaking of the reals whether they are so
definable or not. And I showed you that via parameters there is no
upper limit on the number of reals other than the size of the universe
of discourse itself, and thus this precludes another argument of
impossibility of having uncountably many reals, since there is no
prior limit set on the size of the universe of discourse!
A final word about your project. You tried to prove an "inconsistency"
with the assumption of uncountability of reals, which you couldn't
manage to carry out. And nobody managed and nobody could ever manage
because uncountability of reals is provable in very weak fragments of
Z actually of second order arithmetic, and those are PROVED to be
consistent. However what should that mean! This mean that
uncountability of the reals is a consistent assumption! and thus it is
POSSIBLE that the reals are uncountable, and thus mathematics is to
cover this possibility since it is interesting really. It doesn't mean
at all that we are forced to acknowledge that the reals are
uncountable in the REAL world, no this is not what is entailed. All
what we are presuming here is that we can speak of a model in which
the reals are uncountable, and that is a POSSIBLE model. That's all.
I keep saying that: Mathematics is Discourse about POSSIBLE form. And
I'll speak about that in details in a separate post. Note the emphasis
on "possible". And what determines "possibility" is simply absence of
a contradiction, i.e. consistency. So if you provide a consistent
discourse then you are speaking about a model that might possibly
exist! And thus it would be a legitimate piece of mathematical query.
One would wonder saying is it the job of mathematics to investigate
all possibilities about form even if it flies high up in fantasy. The
answer is yes and no. It is yes in the sense that those possibilities
are mathematical, and it is no in the sense that it is not practical
to do so, so mathematical research will search only those that are
valued as "interesting", and those are matters that rise in
mathematical discourse in almost recursive manner, starting from
obviously interesting issues that seems highly possible to be real,
and then investigating problems of them which would inherit that
interest, and possible solutions to those would be interesting and
those lead to investigating other problems with those solutions which
would become interesting raising possible solutions...problems... and
so on.
Does uncountability of reals raise within this context of mathematical
interest. The answer is YES.
Zuhair