People often talk about "pendulum swings" in attitudes or laws. This seems to me a misleading metaphor.

It's surely true that public opinion and legal rules often move in one direction and then move back in some measure. The perceived excesses of some change -- the sexual revolution, the broadening of tort liability, the changes in perceived differences between men and women, and so on -- will often lead to a reaction that undoes some of the change.

But a pendulum, I think, conveys a different image: It conveys the image of moving back to where you started. My sense is that this very rarely happens. Often the later change will move back only part of the way to the beginning; often it will move to a different place altogether, which shares some aspects of the initial position but which is very different along a different axis. (I've heard this described as "evolution along a spiral," though that phrase might have some baggage attached to it, from Hegel and his heirs.)

And I think there is some harm from the inaccurate image that the pendulum conveys -- it can encourage a mistaken smugness (well, despite all those changes, we're back where we started), resignation (everything is fated to return to what it was), or perception of historical determinism. I don't support literalism in interpreting figurative usages, but the literal meaning of the metaphorical term generally does tend to affect the image that's being sent.