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David,

I’m concerned that your insistence that “inertial acceleration” should be translated as “deviation from geodesic motion” will lead us to a discussion of the difficulty of determining in some cases, by observation, whether a body is deviating from geodesic motion. That’s why I’ve tried to focus on the behavior of test bodies in controlled experiments, in my article, and in response to your comments. There is no ambiguity in distinguishing the behavior of test bodies inside a box being inertially accelerated and a box being accelerated (in a “free-fall”) in a gravitational field. In the first case, they will appear to accelerate to a side of the box, in the second case they will appear to converge toward each other while remaining in the interior of the box.

If we agree that 1) the behavior of test bodies in the experiments just described will be uniquely different in the second case (“free falling” in a detectible gravitational field) from the behavior of test bodies in a box under any other sort of acceleration of the box, if we agree that 2) the behavior of the bodies that converge in the interior of the box are doing so because they are following their geodesics in a gravitational field, then 3) there is no justification of associating gravitation with force.

It is on point 3 that I seem to be getting controversial. You’ve complained repeatedly that I don’t adequately define my terms. My complaint (against everyone I’ve encountered in the field, not just yourself) is that no one will address point 3 directly. You (and/or others) have at this point left the realm of the specific and “phenomenological” in favor of semantics, mathematical abstractions, imaginary situations, situations described in terms that presume phenomena inconsistent with points 1 and 2, allusions to Einstein’s experiments – anything, it seems, but a concrete discussion of how, in terms consistent with points 1 and 2, the leap is made from spacetime geometry, from geodesic motion, to force and energy. If the test bodies - in the experiment where they converge while remaining in the interior of the box - are following their geodesics, Dr. Halliday, they are not being acted upon by a force. And if they are not being acted upon by a force, in what is the most salient example of pure gravitation - a free-fall in a typical, detectible, gravitational field, then the association of gravitation with force needs some earnest, direct justification. Surely that point is controversial, and challenging, to much of current gravitation theory, and should be addressed - directly, without leaps, without abstractions, without digressions, without diversions.