Essential vs. Accidental Ordering

An essential (viz., per se) ordering is an order that causes one to be dependent on the other for its existence; whereas an accidental (viz., per accidents) ordering causes no such dependency.

For example, a human hand is only a human hand insofar as it is properly conjoined to a human organisms in which it serves the whole. If the humans hand is cut off, it is a remnant of a human hand but ceases to be the same part it was when attached. Only by reattaching the hand in a manner that resumes that servitude to the whole will it resume being a human hand. On the other hand, a chair’s legs are parts which do not serve the whole in the same manner: they are also only a part of a chair insofar as they are currently serving a chair, but the leg only loses its identity as a part—not what it fundamentally is. The human hand ceases to be organic matter when cut off (and thusly decomposes); but the cut off wooden, chair leg does not cease to be wooden.