We have all told our dentists where our toothache is.

Thus space is not a relation between substances, but between attributes.
Thus even if you admit that the adherents of substance can be allowed to conceive substance as matter, it is a fraud to slip substance into space on the plea that space expresses relations between substances.

On the face of it space has nothing to do with substances, but only with their attributes.

What I mean is, that if you choose--as I think wrongly--to construe our experience of nature as an awareness of the attributes of substances, we are by this theory precluded from finding any analogous direct relations between substances as disclosed in our experience.

What we do find are relations between the attributes of substances.