Isn't the proposition of a material world supported by the material things in the world around us?
THIS seems to me to have the conclusion in the premise. That's the ENTIRETY of what I was getting at. Everything else was only elaboration about how abstractions like "materialism" or "idealism" come later in life, when culture sticks such ideas into people's heads. My effort to specify "stick with the first person POV" was me trying to avoid any further responses to me that ignored the simple point of logic and involved yapping about either physics or metaphysics or religion.
Is the material world to be considered a premise? We bump against its reality each and every day. So, if a premise, a proven premise.
I think if the materialist Greeks were reacting to a climate of Idealist philosophers, then it wasn't so simple as deriving a materialist metaphysics from the observation of "material" things or objects, as I thought you were suggesting (as if "material" is right there in the experience of phenomena themselves). "Material" is an IDEA that's tacked on top of experience. It'll feel very obvious to a modern who's been exposed to the idea all his life, throughout all his culture.
So I think the Greek materialist philosophers did something way more amazing in deriving "atoms" from their experience than is suggested by a phrase like "Isn't the proposition of a material world supported by the material things in the world around us?" when it was not so obvious-seeming to them that the "things in the world" are material.
The ancient Greeks, as with us all, had a physical world to bump against, interact with and test. How the world is observed to behave, its attributes and properties must be a consideration.
The proposition that the matter is composed of 'atomos' must have been based on observations of the properties of matter, that objects can be reduced, ground down, burnt, etc, to finer and finer particles....a pot becomes a pile shards when broken, shards may be smashed to pieces, the pieces ground to dust, dust to fine powder.