You missed the point. Word meanings are based on conventional usage. Most people can be described as Cartesian (or substance) dualists. Religions are grounded in that assumption, and most people adhere to a religious belief of one sort or another. They use the word "physical" to describe the concrete reality that they can experience through bodily sensations, but they treat thought as a different type of experience--one that has a nonphysical origin. It does not matter whether they are mistaken in that belief. They can still adhere to a model of reality that allows for a plane of existence that is different from what they experience through physical senses. You believe that there is no other "spiritual plane"--that everything is rooted in physical existence. I have no problem with that. I am a physicalist myself in that sense, but I accept the logical possibility of a different model of reality.
Monist. The mind is reducible to the brain.
I understand what you are trying to say here, although I would prefer the expression "brain activity". I agree that mental states correspond to some kinds of physical brain activity, but to equate the mind with brain activity is a genetic fallacy. Water is reducible to H2O, but it has different properties that are not reducible to, or predictable from, the properties of the molecules. Daniel Dennet has referred to this kind of reductionism as
greedy reductionism.
That definition doesn't work very well, given that most English speakers believe that spiritual entities have objective existence. All you are doing here is expressing the opinion that only things with physical properties can exist, but that is just one philosophical point of view.
Two millenia ago, everyone in Greece believed that the sun revolved around the earth. They were wrong irrespective of what they chose to believe.
Technically incorrect, although most Greeks believed that in ancient times.
Aristarchus of Samos proposed a heliocentric model in the 3rd century BC and made some astonishingly accurate claims about astronomical concepts. He was cited by Copernicus for having first proposed heliocentrism. Aristarchus's ideas never really caught on, but they had a few followers, e.g.
Seleucus of Seleucia.
I understand your larger point, but I tried to explain my point to untermensche--that a nonphysical plane of existence is logically possible. There is also the point that emergent properties of systemic activity do not necessarily follow from the components of the system, although they supervene on them. That is, mental events supervene on physical events but are not necessarily equivalent to those physical events.