If simplest = lowest internal variability, I'm gonna go with a vacuum.

One axiom or a single instruction or datapoint.

I vote for strange quark... -1/3 charge, and not much more than a point in space...

I would define simple as having the fewest parts with the fewest interrelationships. I don't think that the attributes of that thing should be part of the definition. Theoretically the simplest thing might have a nearly infinite number of attributes. For this reason I would not disqualify "vaccum" based on the attributes attributed to "quantum foam". However, I think vaccum does not qualify as a "thing". It seems there should be at least one part and vaccum implies nothing. So the simplest thing would be one fundamental indivisible unit of matter/energy- the original atom concept. In modern science it might be a quark, a 1/3 quark, or the fundamental string of string theory, or maybe there is no such thing.

Perhaps you were right Paul,
as all these excellent insights
outline.
Complexity in simplicity.

Now, is there similarly simplicity
within complexity, or is this just
a sign of our propensity of ordering things ?

Arbitrary is in itself an interesting concept.

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