JT, Wolfgang Muckenheim comes across as a finitist. Basically that
means he thinks everything is finite. Virgil Hancher is a dogmatist,
basically he's a self-appointed defender of the orthodoxy, satisfying
his impulse to belittle others with the argument from authority of
modern mathematics. Neither claims much of accomplishing anything,
where "to accomplish" is to develop novel mathematics. Wolfgang wants
to roll it back, Hancher not to roll it forward, basically in the
Bourbaki sense they're negative or strictly negative on the scale of
"accomplish".
Then, here, a definition of field operations for the unit interval is
a bit different than either of those tacks. It's often said that an
interesting property of the complete ordered field is that it's unique
up to isomorphism, as the complete ordered field. It's shown that via
simplest properties of linear functions, a non-real linear function
exists (not a real function, not in some senses of applicability in
the solutions of differential equations linear, but having properties
of continuous and monotone mappings), this function that is invertible
then sees the operations of the field (from abstract algebra, see
properties of fields or field axioms) defined for the interval, from
the reals, (-1,1). With this example then any interval of the reals
centered on the origin has field operations, so equipped with those
operations, each is a field.
And, each is a vector space.
As well then are simple considerations as the unit disc, and Argand or
complex plane, as fields and isomorphic to the complete ordered field.
And, that would be news to some.
Then, what that establishes, is a notion of scaling, of scale, from
the unit, to the infinite, and infinitesimal. For this you might look
to Yaroslav Sergeyev's simple development of powers of infinity as of
scales, the "Infinitarcalcul" of Paul du Bois-Reymond, or even a
variety of developments as seen here.
It might be much different if transfinite cardinals (where powers of
transfinite ordinals are as to scales, but none of their countable
powers reaches the uncountable that modern mathematics has for the
simple continuum), if transfinite cardinals _explained_ something in
physics or were used in continuum analysis for standard results. But,
they aren't. Then, when there's a simple intuition that scaling the
natural integer to fit within the unit, _makes_ a continuous unit
reals, and following up on that intuition: the would-be function
_doesn't_ see the result of uncountability follow, then it's of
interest to a conscientious mathematician: why that is so.
Regards,
Ross Finlayson