oh, for heaven's sake. did I really come across as asking for a bunch of garden-variety pœcilonyms?!

I've always heard it called semantic change. Edward Sapir wrote about drift in his Language but he was talking about the tendency of languages to start changing (semantically, morphologically, syntacticly) and then head in a certain direction (or a set of similar changes cross linguistically.

[Edited typo.]

"poecilonym: synonym; one of a variety of names for a thing "

Phrontistery

I will go now into my study and attempt to assign myself an appropriate penance.

what do you call the natural change seen occuring in other cultural artifacts, such as the law? How about the legality or illegality of slavery?

There are several schools of jurisprudence which ask questions about how the law changes over time (and from place to place). They are remarkably similar to the schools of prescriptivism and descriptivism in linguistics. In analytic jurisprudence, the emphasis is on what the law is, not what it ought to be. It is neutral on issues of morality. As regards slavery, analytic jurisprudence would say something about which legal systems promote it, which tolerate it and which prohibit it (and how) without asking the question "Is slavery a good thing or a bad thing?" This school, it seems to me, is the jurisprudential equivalent of descriptivism. In normative jurisprudence, the emphasis is on what the law ought to be, not what it is. As regards slavery, normative jurisprudence would assert some values or first principles -- e.g. the dignity of every human being, the legal equality of every human being -- and reason from them that slavery is wrong. This school, it seems to me, is the jurisprudential equivalent of prescriptivism. A legal system which moves from permitting slavery to prohibiting it would be seen as improving, from a normative perspective, but only changing, from an analytic perspective. I have oversimplified both of these schools, but one ought not hog too much space in a thread which is not really about jurisprudence.

however, I carefully chose the words sanction and decimate because different operations seem to have been in effect.

that is, decimate gradually changed from a specific small amount (10%) to a generally great amount (almost all). whereas, sanction was almost newborn with two opposing senses (originally a sacred decree or solemn oath --> approval or disapproval)

are these lumped together under semantic change?

are these lumped together under semantic change?

Well, they are all kinds of semantic change. I've just don't remember the terms "semantic dirft" amd "semantic shift" from my readings. As to sanction and decimate, the OED has citations all from within 100 years of one another (16th and 17th centuries) for both. Decimate seems to have been learnedly borrowed into English directly from Latin, but sanction entered from French. Not Norman, but as a new legal term from Parisian French. One of the problems with the study of semantic change, is that semantics doesn't have much of a theoretical framework, having been ignored in the structuralist and generative phases of linguistics rather intensely, to work with, so the terminology may be laxer than in semantics or morpho-phonological studies.

I guess the differentiation (if there be one) between shift and drift pales unto insignificance.

It is not so pale in my eyes. Talking of "shift" you normally focus on the initial and the final state, while "drift" emphasizes the gradualness of the change, i.e. intermediate states are known. I see some parallels in paleo-biology.

Professor R M W Dixon has written a book, The Rise and Fall of Languages, the controversial thesis of which is that languages change at widely variable rates which is best explained by a model of punctuated equilibria. It's a short, fun book to read, and I recommend it.

ran across another site on punctuated equilibrium and although it's not necessarily related to the topic at hand, when a strange interesting phrase comes up twice in one day, I try to take note.
(via a roundabout trip from the fallible fiend...)