Greta wrote: ↑June 8th, 2019, 1:56 amMatter and space are the same thing - just that there's a greater concentration of energy in what we call "matter" than there is in "space". That is, it's all "stuff", in different densities.
There is more than one possibility:
The relationship between space and matter:
1.
identity: space = (spatially extended) matter
[Here, "matter" means "prime matter" or "aether". Matter in the form of massy particles can then be interpreted as a mass-density field with prime matter as its substrate.]
2.
difference: space ≠ (spatially extended) matter.
2.1
attributionalism about space:
space is an attribute of (prime) matter, being its
spatial dimension or extension.
2.2
substantialism about space:
space is a substance
in its own right (so there's a physical substance dualism: the space-substance plus matter-substances):
2.2.1. material substances occupy
regions of space (the space-substance):
There
is space where matter is, so parts of the space-substance are penetrated by material substances. This means that the space-substance isn't "solid" in Locke's sense, i.e. impenetrable.
The space-substance is penetrable (by movable material substances) but immovable.
2.2.2 material substances occupy
holes in space (the space-substance):
There
isn't space where matter is, so parts of the space-substance only surround material substances. This means that the space-substance is "solid" in Locke's sense, i.e. impenetrable. However, when material substances move through it
by displacing parts of it, it behaves like a fluid or liquid substance. (For example, when a stone is thrown into a lake, it sinks and moves through the water by displacing parts of it, with the stone not being penetrated but only surrounded by water.)
The space-substance is impenetrable (by movable material substances) but movable.
2.3
supersubstantialism about space:
(apparent) material substances are (really)
(bundles of) physical properties (quantities) of regions of space (the space-substance).
The space-substance is both impenetrable (by other substances) and immovable. The (apparent) motions of (apparent) material substances "are replaced by spatiotemporal trajectories of successive lightings-up of properties of spatiotemporal regions." (C. B. Martin)
[2.3 can be regarded as including 1: space = prime matter/aether and elementary particles (and all things composed of them) are bundles of physical properties (e.g. mass density) of parts of it. But the parts of the substantial aether aren't reducible to property-bundles, so there's still a difference!]
3.
antisubstantialism or relationalism about space: space is a
structure consisting of spatial relations between material substances (or events). Motion is change of distance relations between material substances.