Existence is ...

How large can an object be and still act like a quantum wave? In theory, any size at all.

Walking is controlled falling. - Robert E.

Existence, to yours truly, is driven by decoherence whereby wavelike superpositions of subatomic bits collapse into particles, thus giving rise to "classic" reality due to inherent noise in the system.

Blame Thomas Young showing why this is so by creating the most beautiful experiment in physics in 1801, the double slit, showing the probabilistic nature of entities being a wave or a particle depending on how said entities are"looked" at. 

Photons or particles of matter (like an electron) produce a wave pattern when two slits are used

It’s a mere speck of matter — a piece of silica crystal no bigger than a virus, levitated in a light beam. But it is almost as motionless as the laws of physics permit.

Two teams of researchers, in Austria and Switzerland, have independently succeeded in freezing such minuscule nanoparticles, just 100 to 140 nanometers across, almost entirely into their lowest-energy quantum state, giving them effectively a temperature just a few millionths of a degree above absolute zero — and fixing them in place with unearthly precision.

Holding a nanoparticle this tightly in a single spot is just the start. The goal is to put these objects into a so-called quantum superposition — where it becomes impossible to say, before measuring them, just where they are. A particle in a superposition could be found in one of two or more places, and you just don’t know which of them it will be until you look. It is perhaps the most startling example of how quantum mechanics seems to insist that our familiar world of objects with definite properties and positions comes into being only through the act of looking at it.

Same double-slit assembly (0.7 mm between slits); in top image, one slit is closed. In the single-slit image, a diffraction pattern (the faint spots on either side of the main band) forms due to the nonzero width of the slit. This diffraction pattern is also seen in the double-slit image, but with many smaller interference fringes.

Buildup of interference pattern from individual particle detections

"Digital" particles giving rise to "analogue" waves show why the duality of existence rings forever true.