The point is that in mathematics
one only gives something up as
for the result of something else.
Then, BKK's "fer sure" is just another
some non-logical axiom applied to the
objects of the numbers or here methods
upon them as result for example in some
simple tractable closed forms and here
for example simple "rational" numbers.
He can find a lot of support for that
since Euclid for example.
However, mathematics writ large has quite
well explored real-valued number systems
for some time, so, BKK's "for sure, for what"
is a usual ostrich's. (As apocryphally
sticks its head in the sand to avoid
the perception of predators.)
"Mathematical continuity" is often and
usually frame in terms of "real-valued
number systems", often per Hardy as both
geometric as of the point-like in lines,
and for example the complete ordered field
with a usual modern curriculum's development
in abstract algebra supporting at least pretty
much in entirety foundations for the integral
calculus.
Then for example then for this "field continuity",
theorists also look to the points in a line
and (more than) the density of rationals besides
(more than) the limits of their series.
Formally, that is....