Abstract Space-Time?

In the previous post, I was quoting Poul Anderson with or without quotation marks. However, I disagree with his use of the word "abstract." "Abstract" is the opposite of "concrete," not of "solid" or "substantial." If space-time preexisted all consciousness and exists independently of any consciousness, then it is "concrete," i.e., it instantiates properties. It does not matter how insubstantial such properties may be. An abstraction is a single property considered in isolation from all others. Thus, we see many white objects and abstract the concept of whiteness. Any particular white object instantiates other properties, e.g., its shape and size, and is seen to exist independently of any of its observers whereas whiteness is an abstract concept existing only in our minds.

Any particular white football or golf ball is solid to the touch. It "really" consists of insubstantial particles and empty spaces but this does not make it abstract like whiteness. And tangible solidity remains one of its perceived properties. If space-time is "unstable," this does not make it abstract. If it were demonstrated that it existed only in our minds, that would make it abstract.