I'll take a stab (I Am Not A Physicist (in fact I couldn't handle the math and moved to CS ;-) ). Parameters or constants in a theory generally have units (i.e

I'll take a stab (I Am Not A Physicist (in fact I couldn't handle the math and moved to CS ;-) ). Parameters or constants in a theory generally have units (i.e. speeds, density, whatever). But lots of things (usually ratios) have no units because they all cancel out. Those are called "dimensionless". Pi is dimensionless, as is e. What the naturalness property seems to be saying is that these dimensionless parameters (which you have to stick into the equations to make the math work out) should all be around the same order of magnitude and not require too much precision. If there is such a parameter that is super huge or super small (in relation to the others) or requires a lot of precision, it's an indication that the theory is incomplete. There should be an observable reason for that difference/precision. If I've gotten that right, then I can see why people would be sceptical of naturalness. If naturalness was correct, I would actually be curious of why it was correct.