Yes, a good point. Obviously everything we have on earth is either naturally occurring or derived from naturally occurring substances. I don't have a problem with the "naturally occurring" part; the issue lies in the "derived" part.
H20 is naturally occurring. It can be lab synthesized. I would not consider lab synthesized water "natural," even though any metric we use to measure/compare it's qualities to natural water would yield no difference.
By "chemical," I meant a substance that is fabricated in a lab using "unnatural" methods. Of course, the phrase "unnatural" is completely subjective, so all I can really do is clarify my interpretation/opinion.
And of course, "natural" doesn't mean it's good for you (or the environment). Crude oil is natural.
From a philosophy standpoint, my rules would be something like this:
I am willing to use anything that is naturally occurring, or anything that is derived from a naturally occurring substance (or substances) using certain "crude" methods such as:
-heating
-cooling
-distillation/condensation/evaporation etc
-mixing, grinding, blending, powdering, dissolving etc (obviously substances may react with one another at this point...)
-cultivating (farming, fermenting, etc
-crude extraction (dissolving etc).
-pressurizing
(this is an incomplete list)
So
as I define it, the following would be "natural" aka "not chemical":
Oil
Gunpowder
Any mined mineral (note some organic growing standards ban some mined substances)
Uranium
(again, an incomplete list)
Obviously my opinions are completely subjective and may seem arbitrary to someone else.