Water is not a gas, not even an air–gas mixture, because it is not a liquid at all. It does not mix with other substances with the same kind of properties. “It is an indeterminate or semi-fluid. It is the least common form of matter. It does not mix with other substances with the same kind of properties.”
So let’s go the other way: Let’s take a step back and ask what are properties? In any particular case, what is water’s ability to be something? This question is a bit trickier than it sounds to answer. If the way we think about water today is a “normal” view, then the answers to the questions above depend heavily on that sort of view. If it’s a “normal” view, then the question is: What are the properties that we look for when we ask for properties in a particular case? If we think of water as a normal form of matter, then properties need to be described in terms of the type of properties that we expect it to have. If we think of water as a normal form of matter, then we need to know a bit more specifically: What makes Water a matter, and what makes Water one of the six known known knowns of matter? And what else can you ask about water? If things are not quite so simple today as they were during the 18th century, then we’ll need to do some careful thinking, and to ask our questions one at a time rather than in a linear manner. If a more linear way of thinking is useful for our purposes, then the question of what is a given property in water is a bit more straightforward.
For example, you’ll recall from Chapter 4 that water is a “form of matter.” What exactly does that mean? What is one part of the “form of matter” of water? Is it the material properties that we attribute to the “form of matter” of water? It is hard to talk about “form of matter” on a case-by-case basis because the categories are all so intertwined. When we refer to “matter” in everyday language, we do so in the sense that one part of our mental apparatus–the part that can think, say, about heat, or about motion, or about fire, or about a cat, or about a book, or about something to do–in some sense is a substance of some class.
On the other hand, what does the physical world consist of? For