I’m up too late in a futile effort to finish some grading, and so very briefly before I get a few hours’ sleep in and rise to finish the job early in the morning:
My piece on “intensive” and “extensive” claims touched briefly on the way that breakdown parallels some of the other basic categories of existing things and of bodies, as organized in various metaphysical systems.
One application of the same argument should be noted specifically: There is a tendency to confuse “essence” as in “what makes a thing what it is” with “the real thing,” and “accident” as in “what is particular to this instance but does not make this thing what it is” with “something optionally added to the real thing.” I apologize for the coarse definitions, but getting into the fine definition of “essence” involves a lot of careful work that is beside the point, for now.
But what happens is that anything, once called “accidental” rather than “essential” is, in our discourse, simply dismissed as “unnecessary” or “wholly optional,” a feature that can be changed at will or omitted.
This is plainly silly, as a moment’s reflection will show.
I am six feet tall. My height is not essential to my humanity, but accidental; many people are human with less, and somewhat fewer with more, height. Being six feet tall, or 5’4″ tall, or 6’10” tall, does not make anyone inhuman; it does not make anyone more human.
So, my height is accidental, and so is yours, to my humanity. Would it follow that we could discard height, or treat it as irrelevant?
Obviously not. To be a human is to be embodied, and a bodily creature is extended in space, and a human creature’s extension in space has height as well as thickness and width. To be human is definitely to have some height; what is accidental is my height, or yours, as measured.
Similarly, many things can change in certain ways, to some extent, because their exact measure, their specification, is accidental; this does not mean they can be dismissed, because at least some of these things are precisely the accidents proper to that kind. Indeed, most essential characteristics (“must have at least some height”) are known to us only by observation of their accidental specifications (six feet, &c).
If we dismiss the accidents because they are not essential, we miss something about each separate being; we also risk distorting our understanding of what is essential, or missing it entirely.