What causes the inertia of an object in classical physics?

[Andrew Mason]

A true point (infinitely small) implies infinite density, which is not possible in classical physics.

What principle or law of classical physics sets an upper limit on the density that a body can have?

AM

 

[Studiot]

I have just appended an (interesting?) additional question about inertia and its causes in this thread:

https://www.physicsforums.com/showthread.php?p=3530129#post3530129

 

[harrylin]

What principle or law of classical physics sets an upper limit on the density that a body can have?
AM

Good one!

Also the electrostatic field energy would be infinite, so that already the creation of an electron would require infinite energy - that does not make any sense. Theorists generally dislike that kind of singularities, but I must admit, that it's a non-binding principle, similar to Occam's razor.

Anyway, I'm pretty sure that electrons were modeled in classical physics as particles with a nominal radius that follows from its charge and its mass, which is assumed to be fully electromagnetic - already before the advent of special relativity.

There even is the label "classical electron radius" which accounts for SR.
- http://en.wikipedia.org/wiki/Classical_electron_radius

What is pertinent for this discussion, is that in classical physics it is rather standard to assume that the inertia of the electron is fully caused by its electromagnetic field.