There are “potential infinite” and “actual infinite” in our present infinite related classical science theory system at least since Zeno’s time, so we can not avoid (logically have) “potential infinitesimal” or “actual infinitesimal” in mathematics. But the confused “infinite”, confused “potential infinite--actual infinite” have being creating a lot troubles (such as infinite related paradoxes) when we are treating (cognizing) some “infinite things” in mathematics. The Harmonic Series Paradox is a typical example:
1, no one cares what y---->0 (Un---->0)in Harmonic Series means-------“potential infinitesimal” or “actual infinitisimal”and where do they locate in number system,
2, no one cares what differences between y---->0 (Un---->0) in Harmonic Series and y---->0 (dx ---->0) in calculus,
3, no one cares whether or not we should have different ways when treating “potential infinitesimal” or “actual infinitesimal”.
4, no one cares whether or not we can really produce infinite items each bigger than 1/2, or 100, or 1000000, or 10000000000000000000,… from the Un--->0 Harmonic Series and no one cares the exact (how many) items being consumed for just the first 10000000000000000000 from Harmonic Series.
The suspended infinite related paradoxes have been disclosing the fundamental defects of “infinite theory, limit theory, number theory” in present infinite related science theory system.