The answer is intuitively simple but rather difficult to explain logically. We must construct the universe out of perceptual-visual blocks. It must be constructed out of elementary, essential principles which are observable to any man who can see (or visualize somehow even if blind). I mean here geometric entities.
These are the only things that are transferable from one mind to another unambiguously.
Yes ... mathematics can be unambiguous. However, it is unambiguous when denoting the number of geometric entities. It is the description of the blocks and their activities ... but not the thing itself.If we do not begin at the perceptual level, we are left with the manipulation of "identifiers" - (words made up to denote something which is inferred to be there but which we cannot as yet explain in terms of perceptual-visual entities).
An explanation of gravity would require that we look into the phenomena and describe it in terms of what geometry does or is under specific circumstances.
Similarly, the term "mass" is an identifier. Yes, it is a perceptual entity by way of feeling (as when we move a large object). However, we are creatures of vision and are thus constrained to put everything in terms of visual entities. We cannot mix visual, tactile, auditory, olfactory, taste and balance perceptions as logical primaries of existence because there is no "calculus of interactivity" by which we can relate one sense to another. We simply assume at the outset that a smell, for instance, is composed of geometric entities which perform some such activities which are then perceived as smell, i.e. to explain ... we always go back to geometry.
So if we wish to explain mass and gravity in a satisfactory way, we have to show some geometric entity which does something which we can see would produce the effect we perceive in the real world.
I think it should then be apparent to the reader why I would object to an explanation of existence which proposed something like this -
Property designated as Yb acts on entity X through the intermediary of the Zetac12 process ... thus producing the phenomena we call gravity.Obviously, men will want to have Yb, X and Zetac12 explained
things they can see instances of in the real world (like point, line, plane, rotation, acceleration, wave, etc.). And if they don't get such an explanation, they will continue seeking an explanation until they get one on those terms (or until a "proof of impossibility" is obtained as may be the case with some quantum effects). With any other type, honest men will sense that they are being "had" - as by a conman.
A final note here:
There will always be some who disagree with any explanation no matter how all inclusive and rigorous. And there are others who refuse outright to entertain anything more than "God did it". I do not wish to attempt such an impossibility as to convince all men. Rather, I wish to explain phenomena to myself as best I am able. Should anyone else benefit from that attempt, so much the better (provided I am, in the end, right).