On Monday, November 11, 2019 at 3:28:05 AM UTC-6, Bruno Marchal wrote: > > > On 10 Nov 2019, at 20:09, Lawrence Crowell <goldenfield...@gmail.com > <javascript:>> wrote: > > On Sunday, November 10, 2019 at 6:17:10 AM UTC-6, Bruno Marchal wrote: >> >> >> On 9 Nov 2019, at 02:22, Lawrence Crowell <goldenfield...@gmail.com> >> wrote: >> >> We can think of infinitesimals as a manifestation of Gödel's theorem with >> Peano number theory. There is nothing odd that is going to happen with this >> number theory, but no matter how much we count we never reach "infinity." >> We have then an issue of ω-consistency, and to completeness. To make this >> complete we must then say there exists an element that has no successor. We >> can now take this "supernatural number" and take the reciprocal of it >> within the field of rationals or reals. This is in a way what >> infinitesimals are. These are a way that Robinson numbers are constructed. >> These are as "real" in a sense, just as imaginary numbers are. They are >> only pure fictions if one stays strictly within the Peano number theory. >> They also have incredible utility in that the whole topological set theory >> foundation for algebraic geometry and topology is based on this. >> >> >> Roughly thinking, I agree. It corroborates my feeling that first order >> logic is science, and second-order logic is philosophy. Useful philosophy, >> note, but useful fiction also. >> >> Bruno >> >> > The key word is useful. Infinitesimals are immensely useful in calculus > and point-set topology. > > > Which infinitesimals? The informal one by Newton or Leibniz? Their > recovering in non-standard analysis? > Of in synthetic (category based) geometry? > > If one is sticking to a more formal approach then Leibniz Really Weierstrass is the guy who got this straight.
> Personally, despite I am logician, I don’t really believe in non standard > analysis. I find the Cauchy sequences more useful, and directly > understandable (the “new” infinitesimal requires an appendix in either > mathematical logic or in category theory). > > These things are not about belief or nonbelief. They are formal models, and as I see it one works with any particular model if it is useful. > > > It provide a proof of the mean value theorem in calculus, which in higher > dimension is Stokes' rule that in the language of forms lends itself to > algebraic topology. > > > Abstract topology is enough here, in the Kolmogorov topological abstract > spaces. You don’t need formal infinitesimal to have a mean value theorem in > calculus. I guess you are OK with this. > > > The MVT relies upon calculus f'(c) = (f(a) - f(b))/(a - b) or the integral form ∫f(x)dx = f(c)(a - b) for b to a limits in integral. So infinitesimals are there at least implicitly. When it comes to point set topology I prefer to get past that as quickly as possible and get to cohomology, homotopy or cobordism. > > Something that useful as I see it has some sort of ontology to it, even if > it is in the abstract sense of mathematics. > > > Like physics, when we assume mechanism, it exists in the phenomenological > sense, which is the case of all interesting thing. But to solve the > mind-body problem, we need to be clear on the ontology, and with mechanism, > the natural numbers (accompanied by their usual + and * laws) or anything > Turing equivalent is enough, and cannot be extended, without making the > phenomenology exploding (full of “white rabbits”). > > Bruno > > I don't have thoughts on the mind-body problem. I have no particular theory about consciousness or anything related. LC -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/6ce67a53-c135-46e3-9dc1-9937acf530e4%40googlegroups.com.
