I don't believe in zero or negativity as a rational concept. Nothing does not exist; to negate something is rather a convenient way of affirming its existence elsewhere or as arranged in another order. So: the idea of something being completely devoid of, or separate from, -any- existent property seems to be impossible. I could not say if I went for technical accuracy, then, that anything is immaterial, or massless, or inertialess. For instance, I think this concept of "antimatter" is implausible. I'd rather conject that existence as a whole is completely filled without gaps by one substance, and the analysis of this is the spectrum of relative diversity. (How do you move on from such a point? There's no first step 'down' from infinity, is there?) But from that perspective I would argue over classification.

It's really messing with my head, this trying to be a monist.