People believe that 0 (zero) has played different rolls as a kind of special form of number (substantiality) in our science, such as:
(1) A kind of reference ------- generator, middle, neutral, beginner, origin, placeholder, marker,…,
(2) Absolutely non-existent ------- without numerical value meaning, the negation of being, objectively nothingness,
(3) Relatively non-existent ------- with numerical value meaning, subjectively nothingness, the approximate nothingness, the result of infinitesimal limit , ….
Lacking the systematic cognition to 0 (zero), no one in the world now can answer following question scientifically and this is the very reason for many “infinite related paradox families” in present classical infinite related mathematics:
Are “dx--->0 infinitesimal” in Calculus and “Un--->0 infinitesimal” in Harmonic Series the same things? If ”yes”, why we have totally different operations on them? If ”no”, what are the differences and how to treat them differently and why?